Title:
SAFETY AID FOR SLOPING ROOF
Kind Code:
A1


Abstract:
The aid provides a manner of supporting a plank, on a roof, for workers to stand on. The plank is carried on plank-jacks, but the plank-jacks are not attached directly to the roof joists. Rather, the plank-jacks are suspended via rope-slings from a pair of ridge saddles, which are firmly and safely secured to the ridge of the roof. The rope-slings are adjustable, and the worker can very readily adjust the working level of the plank.



Inventors:
Leendertse, Paul David (Waterloo, CA)
Application Number:
11/464261
Publication Date:
02/15/2007
Filing Date:
08/14/2006
Primary Class:
International Classes:
E04G3/26; E04G5/04; E04G21/32
View Patent Images:
Related US Applications:
20070187184Scissors lift utility tray assemblyAugust, 2007Nasuti et al.
20090008187Attachment and storage system for an extendible ladderJanuary, 2009Garelick
20060151243Parapet mounted net systemJuly, 2006Rexroad
20020079166Safety latch device for an extension ladder systemJune, 2002Gaik
20030037990ROOF AND SHINGLE PROTECTOR ARRANGEMENTFebruary, 2003Vincent Jr.
20090078827FOLDABLE STEP FOR A VEHICLE, AND A VEHICLE PROVIDED WITH SUCH A STEP UNITMarch, 2009Martin
20080035427Collapsible work horseFebruary, 2008Fowler
20060054387Saftey harnessMarch, 2006Fortin
20090188751FALL PROTECTION DEVICEJuly, 2009Gilliam
20040003967Order picker truck with a zoned operator platform coveringJanuary, 2004Fett et al.
20040144595Ladder stabilisersJuly, 2004Hanison



Primary Examiner:
CHIN-SHUE, ALVIN CONSTANTINE
Attorney, Agent or Firm:
PAUL DAVID LEENDERTSE (WATERLOO ONTARIO, CA)
Claims:
1. Apparatus for aiding a worker working on a sloping roof, wherein: [2] the apparatus includes left and right plank-jacks, which are physically capable of being used with a plank having length and thickness, and having a width of at least six inches; [3] in respect of each one of the plank-jacks: [4] the plank-jack has a base and a platform; [5] the base of the plank-jack is physically capable of resting on and against the sloping roof; [6] the platform of the plank-jack is physically capable of being firmly fastened underneath the plank, across the width of the plank; [7] the apparatus includes an attachment-support means, by means of which a rope-sling can be attached to the apparatus; and [8] the apparatus is physically capable, when firmly fastened to the plank, and when a rope-sling is attached to the attachment-support means, of transmitting to the rope-sling the weight of the plank-jacks, of the plank, and of a person standing on the plank.

2. As in claim 1, wherein, each plank-jack weighs less than ten pounds, and preferably less than five pounds.

3. As in claim 1, wherein the apparatus includes a left hook-receiving means and a right hook-receiving means, which are unitary respectively with the left and right plank-jacks, and by which respective left and right rope-slings can be hooked to the apparatus and can be unhooked from the apparatus.

4. As in claim 1, wherein, in respect of each plank-jack, the plank-jack includes a unitary strip of metal, suitably bent such that a first portion of the strip of metal forms the platform and a second portion of the same strip of metal forms the base.

5. As in claim 4, wherein the hook-receiving means comprises a ring, and the ring is attached to the strip of metal.

6. As in claim 4, wherein the base of the plank-jack is of such physical configuration as to be capable of lying flat against, and in direct touching contact with, the sloping roof.

7. As in claim 6, wherein the base of the plank-jack includes a protective bumper of relatively soft material, which, in use, lies between the strip of metal and the roof.

8. As in claim 1, wherein: [2] the apparatus includes the said plank; [3] the platform is firmly fastened underneath the plank, across the width of the plank; [4] the worker being capable of picking up the plank manually and of carrying the plank up a ladder, the apparatus is of such negligible weight, compared with the plank, that, when the two plank-jacks are firmly fastened underneath the plank, the assembly of plank and plank-jacks jacks is capable of being picked up, and of being carried up a ladder, as a unit, manually by the said worker; [5] the apparatus includes an attachment-support means, by means of which a rope-sling can be attached to the apparatus; and [6] the apparatus is physically capable, when a rope-sling is attached to the attachment-support means, of transmitting to the rope-sling the weight of the plank-jacks, of the plank, and of a person standing on the plank.

9. As in claim 8, wherein: [2] the apparatus also includes left and right rope-slings and left and right roof-fixtures; [3] in respect of each rope-sling, the rope sling: [4] includes a top-attachment-structure at an upper-end; [5] includes a bottom-attachment-structure at a lower-end; [6] includes a length of rope; and [7] includes a rope-clamp; [8] is of such physical structure that the distance between the upper-end and the lower-end of the rope-sling can be shortened or lengthened; and [9] is of such physical structure that, while a force is applied in the tensile sense tending to separate the lower-end from the upper-end, the rope-clamp grips the rope and thereby prevents the lower-end from moving away from the upper-end; [10] in respect of each roof-fixture, the roof-fixture: [11] includes a means for attaching the top-attachment-structure of the rope-sling to the roof-fixture; and [12] includes a means for attaching the roof-fixture to a roof; [13] the top-attachment-structure of the rope-sling lies attached to the roof-fixture; and [14] the bottom-attachment-structure of the rope-sling lies attached to the attachment-support-means.

10. As in claim 9, wherein, in respect of each plank-jack, the configuration of the plank-jack is such that: [2] when the base is resting against the roof, and the plank is attached to the platform, the platform of the plank-jack provides support for holding the plank in an at least roughly horizontal plane, and for preventing the plank from tipping relative to the roof; and [3] the plank-jack provides the said support simply by resting on the roof, without being attached to the roof.

11. As in claim 9, wherein the roof-fixture comprises a ridge-saddle.

12. Procedure for aiding a person working on a sloping roof, including: [2] providing the apparatus of claim 8; [3] attaching the roof-fixtures to the roof in a spaced-apart relationship; [4] attaching the bottom-attachment structures of the rope-slings respectively to the plank-jacks; [5] attaching the top-attachment-structures of the rope-slings respectively to the roof-fixtures.

13. Procedure for supporting a worker on a sloping roof, including: [2] providing a rope-sling, which includes: [3] a top attachment-structure and a bottom attachment-structure; [4] a main-length, being the distance between the attachment-structures when under tension; [5] a lock, which is effective, at least so long as there is tension applied to the rope-sling between the attachment-structures, to lock the rope-sling and to prevent the main-length of the rope-sling from extending; [6] an operable unlocker, which is effective, when operated, to unlock the lock, and thereby to enable the main-length of the rope-sling to be changed; [7] providing a roof-saddle attached to the roof, which includes a saddle-sling-attachment means for detachably attaching the top attachment-structure of the rope-sling to the roof-saddle; [9] attaching the top attachment-structure of the rope-sling to the roof-saddle; [10] providing a plank-jack-sub-assembly, which includes: [11] a plank, plus a plank-jack; [12] a plank-sling-attachment means for detachably attaching the bottom attachment-structure of the rope-sling to the plank; [13] the plank-jack includes a jack-platform and a jack-base; [14] the jack-platform lies at such angle relative to the jack-base that, when the jack-base is resting flat against the sloping roof, the jack-platform is at least approximately horizontal; [15] the plank is firmly fixed, width-wise, to the jack-platform; [16] the plank-jack-sub-assembly has the characteristic of being light enough and manageable enough to be picked up and carried up a ladder, as a whole unit; [17] providing the plank-jack-sub-assembly, as a whole unit, away from the roof; [18] lifting the plank-jack-sub-assembly, as a unit, onto the roof; and [19] attaching the bottom attachment-structure of the rope-sling to the plank-sling-attachment means of the plank-jack.

14. As in claim 13, including the worker manually picking up and carrying the plank-jack-sub-assembly, as a whole unit, up a ladder, onto the roof.

15. As in claim 14, including: [2] the worker having donned a safety harness, securing the safety-harness to a harness-saddle, which is secured to the roof, where the safety-harness and the harness-saddle are capable of supporting the whole of the worker's weight; and [3] the worker then standing on the plank, and resting their weight onto the plank.

16. As in claim 15, wherein the procedure includes the worker adjusting the position of the plank on the roof, as follows: [2] the worker transferring their weight away from the plank, thereby relieving their weight from the plank; [3] with their weight relieved from the plank, the worker operating the unlocker; [4] with the lock unlocked, the worker changing the main-length of the rope-sling; and [5] the worker then transferring their weight back onto the plank.

17. As in claim 13, including: [2] providing left and right roof-saddles attached to the roof; [3] providing left and right rope-slings away from the roof; [4] the worker carrying the rope-slings up onto the roof, and attaching them to the roof-saddles; [5] providing the plank-jack-sub-assembly, as a unit, away from the roof; [6] the worker carrying the plank-jack-sub-assembly up onto the roof, and attaching the rope-slings thereto.

Description:

This invention relates to a system for aiding a roof-worker when carrying out tasks on a sloping roof.

BACKGROUND TO THE INVENTION

The dangers of working on a sloping roof—during construction work for example—are all too clear. Numerous systems have been proposed, and are in place, for safeguarding workers. However, these systems involve compromises between safety and convenience, and it is left to supervisors to check that the systems are constantly in use. Traditionally, the systems that offer convenience are not inherently safe, and the systems that offer safety are not inherently convenient.

It is an aim of the invention to provide a system that is highly convenient for the worker to use, and at the same time is inherently safe.

The conventional screwed-down ridge-saddle does represent an inherently safe manner of securement, in that it is shaped to fit the ridge of the roof. The ridge-saddle takes support from the geometry of the ridge, so that even if the fixing screws (or nails) might be loose, they are unlikely to be actually pulled out. This type of inherent safety is in keeping with the aims of the invention.

The conventional ridge-saddle includes a ring, and typically the roof worker attaches a personal safety harness to the ring.

By contrast, conventional plank-jacks are not inherently secure. Traditionally, these jacks are nailed to the sloping roof, the nails passing through the plywood sheathing and into the roof joists. The problem with this is that the worker can think the jack is secure, but actually it is only nailed to the plywood sheath panel, not to the joist. It would be almost less dangerous for the jack to be secured not at all, than for the jack to appear to be secure when it is not actually and fully secure. Many injuries have been caused by plank-jacks giving way unexpectedly.

GENERAL FEATURES OF THE INVENTION

The invention makes use of the kind of inherent security that is present in the conventional ridge-saddle. The plank-jacks are preferably not attached to the roof at all, but rather are supported on rope-slings from the ridge-saddles.

The rope-slings are adjustable as to length, whereby the worker can very readily adjust the level of the plank. The worker can simply readjust the level of the plank, as work progresses, over the whole surface of the roof. As compared with the conventional ways by which workers can safely carry out tasks on roofs, the system of the invention permits large savings in time, and efficiency.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

By way of further explanation of the invention, exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectioned side elevation of a roof of a building under construction, to which a system that embodies the invention is applied.

FIG. 2 is a front view of a ridge-saddle component used in the system.

FIG. 3 is a pictorial view of the roof of FIG. 1, showing more of the components used in the system;

FIG. 4 is a view corresponding to FIG. 1, at another location on the roof.

FIG. 5 is a front view of a plank-jack component used in the system.

FIG. 6 is a view similar to FIG. 4, showing some aspects of the geometry of the plank-jack.

FIG. 7 is a view similar to FIG. 6, showing another plank-jack.

The scope of the invention is defined by the accompanying claims, and not necessarily by specific features of exemplary embodiments.

The drawings show items of apparatus that have been configured and arranged for use in a roof-working aid system that embodies the invention. The apparatus as shown in the drawings is intended to be used after the frame of the roof has been erected and is secure. The safety aspects of the working aid system make use of the integrity of the roof frame.

The aid system can be used for the task of applying the plywood sheath or cover over the frame, and for the task of attaching the shingles or roofing tiles over the cover. The system can also be used after the roof has been finished, for example for such tasks as repairing or re-shingling a roof, for installing skylights, and the like.

In FIG. 1, a sloping roof 20 comprises a frame of wooden studs 23, to which a cover sheet 24 of plywood has been secured. The support system makes use of a ridge-saddle 25 (shown in side view in FIG. 2). The worker secures the ridge-saddle 25 to the studs at the ridge of the roof, e.g by screws 26.

The ridge-saddle 25 includes a ridge-ring 27. The ridge-saddle, with ridge-ring, is conventional in itself, being a proprietary safety item that is in widespread use for receiving safety harnesses and other items, for on-roof work. In the traditional usage of the ridge-saddle, the worker, having donned a safety harness, snags a hook of the safety harness onto the ridge-ring 27 of the ridge-saddle 25.

As shown in FIG. 3, the worker secures two of the ridge-saddles 25 to the roof ridge in a spaced apart relationship.

The roof-working aid system also makes use of a plank 28. Typically, this would be of wood, e.g two inches by ten inches (one inch=2.54 cm), and e.g ten feet long (1 foot=30.48 cm). To the plank 28 are secured two plank-jacks 29. One of the plank-jacks 29 is shown in FIGS. 4,5.

The apparatus being configured for use in the roof-working aid system of the invention, the plank-jack 29 need not be fastened directly to the roof. The system makes use of the fact that the ridge-saddle 25 is secured to the roof—the ridge-saddle has to be provided, and secured, in any event (often, its provision is dictated by safety codes), when persons are working on the roof, to support the safety harnesses of the workers.

The plank-jack 29 includes a rigid steel strip, which is bent to the profile shape as shown in FIG. 4. This shape includes a base 30, a brace 32, and a platform 34. The plank 28 is bolted to the platform 34. At the top end of the base 30, the strip is formed with an eye 31, in which is secured a plank-ring 35. The platform 34 is fastened to the base 30, at 33; the manner of fastening may be permanent (e.g by welding), or may be dismantlable, whereby the angle the platform 34 (and the plank 28) makes with the base 30 can be adjusted.

The plank-ring 35 is suspended from the ridge-ring 27 by means of a rope-sling 36. The rope-sling 36 includes a rope 37, and an adjustable rope-clamp 38. The upper end of the rope 37 terminates at a top-hook 39, and an upper hand-grip 40 facilitates manipulation of the top-hook 39 into engagement with the ridge-ring 27. A lower hand-grip 43 is fastened to the rope-clamp 38, and terminates in a-bottom-hook 45, which is engageable with the plank-ring 27.

The rope 37 passes between clamping members inside the rope-clamp 38, whereby when the rope-sling 36 is loaded in tension, as shown in FIG. 3, the rope-clamp 38 grips the rope 37, preventing elongation of the rope-sling 36. The length of the rope-sling 36 (i.e. the distance from the top-hook 39 to the bottom-hook 45) can be shortened by lifting the tail 46 of the rope 37, and pulling the tail 46 upwards relative to the rope-clamp 38. This action releases the clamping members inside the rope-clamp mechanism enough to enable the rope to slide through the rope-clamp 38.

It is possible to shorten the rope-sling—by pulling upwards on the tail 46—even though there is still tension in the rope 37. To lengthen the rope-sling, this is done by first taking away tension in the portion of the rope that passes through the rope-clamp 38. Now, the rope 37 can slide through the rope-clamp 38 in the lengthening direction—or in the shortening direction, of course. The worker can readily support their weight by holding on to the rope 37, above the rope-clamp 38, with one hand; the other hand can then be used to manipulate the slack rope (i.e. the portion of the rope below the first hand) through the rope-clamp. As soon as the rope-clamp 38 is put (back) in tension, the clamping members grip the rope and prevent further elongation. The rope-sling 36, as described, is conventional in itself, being a proprietary safety item that is in widespread use for on-roof work.

In order to carry out the task of affixing shingles to the roof, the worker first positions the apparatus with the plank 28 close to the eave line 47, as shown in FIG. 3. (Note: the lines 48 are often actually marked on the roof, being carefully laid out as an aid to correctly positioning the shingles.) The worker now affixes the bottom row of shingles while squatting or kneeling on the plank, and leaning downwards. Once the bottom row of shingles is in place, the worker then lowers the plank, so now the plank 28 is resting on the shingles just installed.

As mentioned, the worker cannot lower the plank 28 (i.e. cannot lengthen the rope-sling 36) until all weight is taken off the rope-clamp. The worker can make use of the fact that they have a safety harness, which is hooked into the ridge-ring 27; the worker can support themself with one hand by hanging from the safety harness, to take their weight off the plank, for a few moments, to enable lowering the plank. Of course, shingling is done from the bottom up, which entails progressively shortening the rope-slings 36. The need to lengthen the rope-slings 36 arises only occasionally.

With the plank 28 set at the right height, the worker can stand on the plank, and can proceed to install the rest of the shingles on the roof. From time to time, as they proceed up the roof, the worker simply shortens the (two) rope-slings 36 and raises the plank 28. Thus, the worker would shorten the rope-slings 36 after having installed a few rows of shingles. It may be noted that it is so easy, with the system as described herein, as compared with traditional systems, for the worker to shorten the rope-slings, that the worker might even contemplate shortening the rope-slings after each row. It has been found that workers can do this with very little practice, in a very rapid and efficient manner. Complete safety can never be guaranteed, but it can be asserted that the chance of an accident, when using the apparatus, even if the worker approaches the work perhaps with less than the usual skill and attentiveness, is very much reduced, as compared with the traditional manner by which roofing shingles are installed.

On a gently sloping roof, i.e. a roof on which the worker can walk about, the worker can simply stand on the roof (as distinct from hanging on their safety-harness), thereby relieving the plank and the rope-clamp of weight, and enabling the length of the rope-sling to be adjusted.

In FIG. 4, the base 30 of the plank-jack 29 is shown resting flat against the sloping roof 20. In the traditional systems, the equipment used was highly likely to mark and mar the just-laid shingles upon which it rests, and, though reduced, this tendency can still be present in the present system. So, a bumper of e.g rubber may be secured to the undersurface of the base 30, to protect the shingles.

The plank 28 being attached to the plank-jack 29, as mentioned the angle 49 (FIG. 4) at which the plank rests is determined by the angle 50 between the base 30 and the platform 34. The angle 49 at which the plank rests is determined also, of course, by the slope of the roof. If the slope of the roof were steeper, in FIG. 4, the plank would be tilted over in the clockwise sense. From the safety standpoint, the plank should not be angled further in the clockwise sense than horizontal; in other words, the apparatus should not be used when the slope of the roof is steeper than the angle 50. It is not so much of a safety problem for the plank to be tipped or tilted the other way (i.e. inwards). To suit most roofs likely to be encountered, the angle 50 should be between forty-five and thirty degrees.

Preferably, the width of the plank 28 should be no more than the width of the platform 34; if the plank were to overhang to the right, in FIG. 4, more than about say an inch, that might be unsafe, in that the worker might be able to apply their weight to the plank in such manner as to tip or tilt the plank clockwise (outwards). Preferably also, the base 32 should be so arranged as to make it difficult or impossible for the worker to so apply weight to the plank that the plank tends to tip clockwise. The length of the base 30 should be such that the lowermost extremity 53 at which the base touches the roof lies well to the right of the centreline of the plank. However, it is not difficult to achieve the correct dimensions and configuration such that the plank is very stable and safe.

FIG. 6 shows the relationships the designer should bear in mind. The prudent designer will cater for the worker standing such that their weight W acts at the outermost edge 56 of the plank 28. Standing thus, the worker applies a tipping moment to the plank, equal to the worker's weight W multiplied by the overhang distance H. This tipping moment tends to make the plank-jack 29, and the plank 28, pivot clockwise about the point 53. The tipping moment is resisted by the moment tending to tip the plank the other way, which is equal to the tension T in the rope-sling 36 multiplied by the offset distance R. If clockwise tipping were to start, the offset distance would increase, so that a position of equilibrium presumably would be reached where the product of T×R is equal to the product of W×H. However, even though tipping right over might be a very remote possibility, of course any tipping at all is undesirable. The offset R therefore should be large enough that the equilibrium position of the apparatus is with the base 30 of the plank-jack 29 resting flat against the roof surface 20, no matter where the worker stands on the plank 28.

Preferably, the designer should set the distance R at between one inch and four inches, and the distance H at no more than six inches (and preferably zero inches).

When fixing the bottom-most row of shingles, the worker might position the plank-jacks a few inches above where the bottom row will be affixed; then, the worker would kneel on the plank and would lean out and over the plank, and would reach down, below the level of the plank, to carry out the work of fixing the lower-most row of shingles. The designer should make sure that the plank remains stable even under this manner of loading. Again, it is recognised that a geometry that has that result, over a wide range of roof slopes, is easy enough to engineer.

It might be possible, theoretically, for the plank to tip the other way, i.e to rotate anti-clockwise in FIG. 4. However, it is simple to engineer the plank-jack such that the possibility of such a condition arising is very remote.

It may be noted that, in the traditional plank-jacks, the plank-jack was nailed to the roof. Therefore, although the plank-jack was much less secure, as explained, as regards the possibility of its (suddenly) tearing free, at least, while it was in place, the nailed-down plank-jack did not tend to tip. The new plank-jack, as described herein, is not nailed to, or otherwise attached directly to, the roof, and therefore the designer has to take precautions against tipping. However, as explained, it is simple for the designer to ensure that tipping is not a problem.

It will be understood that the plank could not conveniently be attached to the plank-jacks, in a system in which the plank-jacks were fastened (e.g by nails) to the roof, because the plank would be in the way when inserting (and especially when removing) the nails from underneath the plank. In the present system, the plank-jacks should be securely bolted to the plank-jacks, and may be left so for the life of the plank. (Wooden) planks have a relatively short,life, but the (metal) plank-jacks can be expected to last indefinitely.

As mentioned, the base 30 of the jack may be provided with a soft bumper for actual contact with the roof. The base 30 may also be provided with upturned ends, or ski-ends, as shown at 57 in FIG. 7, in order to alleviate the possibility of the ends of the base digging in and marring the surface of the roof.

As shown in FIG. 5, the plank-jacks 29 should be positioned at almost the very ends of the plank 28; if the plank were to overhang outside the plank-jack 29, the worker might upset the plank if they were to stand on the overhanging portion. On the other hand, a sixteen-ft long ten-by-two wooden plank weighs almost as much as the worker; so the risk of the plank being upset if the worker were to stand on the overhanging end is more theoretical than real. In fact, many roofs are angled and gabled such that the ability of the worker to stand on a portion of the plank that lies a foot or two outside the plank-jack can be very convenient. Of course, the worker should not be encouraged to think that standing outside the plank-jacks is risk-free. But the temptation to do so is high, and with the present design it is recognised that such standing is not particularly risky. Again, at most work sites, there is a rule that roof-workers must always be secured by a safety harness.

The strip of metal that forms the plank-jack 29, i.e the component to which the plank is attached, as shown is directly attached to the plank-ring 35. However, that is not essential; in an alternative version, the plank-ring is carried on a separate bracket that is bolted to the plank. In FIG. 7, the plank-ring is formed from an eye-bolt 58, which passes through a hole drilled in the plank, aligned with a corresponding hole in the platform 34. The strip of metal preferably is between one inch and four inches wide.

The plank need not be attached to the plank-jacks by being through-bolted thereto, as shown in the drawings. However, the plank should be firmly fastened to the plank-jacks; that is to say, when fastened, the plank-jacks should be incapable of independent movement with respect to the plank, under all conditions of loading, including a certain degree of abusive loading, such as might be encountered in use.

The system described herein is for aiding a person to carry out tasks on a sloping roof. It will be appreciated that the task of setting up the apparatus is a key aspect as regards the efficiency with which the overall roofing task can be carried out. The smaller the number of journeys up and down the ladder that it takes for the worker to set up the equipment, the better, from the efficiency standpoint.

With the present system, typically, the worker can carry the equipment up in just two journeys up the ladder, as follows. It will usually be the case that the ridge-saddles 27 are already securely attached to the ridge of the roof, but the worker should first see to it that the ridge-saddles are strategically placed where needed on the roof. The worker prepares the (two) rope-slings on the ground. The worker can easily pick up the rope-slings manually, and can carry them up the ladder onto the roof. The worker hooks the top-attachment-points of the rope-slings to the ridge-saddles. The worker can also easily carry any odds and ends of equipment, on this journey.

Next, the worker returns to the ground, and prepares the plank and the plank-jacks, on the ground. The plank-jacks might already be bolted to the plank, or the worker can perform this task at this point, and should at any rate ensure that the bolts are tight and secure. When the plank-jack-sub-assembly has been constructed and inspected, the worker picks up the plank-jack-sub-assembly, as a whole unit, and carries the sub-assembly up the ladder. The worker should not be required to carry anything else other than the plank-jack-sub-assembly, on this journey. Of course, not every person can carry a sixteen-ft long, 100-pound plank up a ladder, but roof-workers typically are readily capable of such a task. The extra weight of the plank-jacks is only a few pounds, which makes virtually no difference to whether the worker can carry the sub-assembly up the ladder.

When using the present system, it is a simple matter also for the worker, after completing a section of roof, to move the equipment to the next section. The worker can unhook the left rope-sling from the left ridge-saddle, and hook the left rope-sling, temporarily, to the right ridge-saddle, so both rope-slings are suspended from the right ridge-saddle. Then, the worker unhooks the right rope-sling, and moves it to the next available ridge-saddle to the right, and the task of moving the equipment is complete.

With other systems, by contrast, the worker is forced to make three or even four journeys up and down the ladder in order to take the equipment from the ground onto the roof. With other systems, also, the worker must take at least part of the equipment down the ladder, and back up again, in order to move it to a new location on the roof. On a typical roof, it is rarely possible to get away with moving the equipment only six times, and more times are required if the roof is large and/or complicated. Therefore, the importance will be appreciated of the rapidity with which the equipment can (safely) be deployed.