of a railroad track or crane truck, or in any
position where they would impede or prevent
access to fire-fighting equipment.
When materials are being loaded or unloaded
from any vehicle by crane, the vehicle
operators and all other persons, except the
rigging crew, should stand clear.
When materials are placed in work or storage
areas, dunnage or shoring must be provided, as
necessary, to prevent tipping of the load or
shifting of the materials.
All crew members must stand clear of loads
that tend to spread out when landed.
When slings are being heaved out from under a
load, all crew members must stand clear to
avoid a backlash, and also to avoid a toppling
or a tip of the load, which might be caused by
fouling of a sling.
The shear legs are formed by crossing two
timbers, poles, planks, pipes, or steel bars and lashing
or bolting them together near the top. A sling is
suspended horn the lashed intersection and is used as
a means of supporting the load tackle system
(figure 4-39). In addition to the name shear legs, this
rig often is referred to simply as a shears. (It has
also been called an A-frame.)
The shear legs are used to lift heavy machinery
and other bulky objects. They may also be used as
end supports of a cableway and highline. The fact
that the shears can be quickly assembled and erected
is a major reason why they are used in field work.
A shears requires only two guy lines and can be
used for working at a forward angle. The forward guy
does not have much strain imposed on it during
hoisting. This guy is used primarily as an aid in
adjusting the drift of the shears and in keeping the top
of the rig steady in hoisting or placing a load. The
after guy is a very important part of the shears
rigging, as it is under considerable strain when
hoisting. It should be designed for a strength equal to
one-half the load to be lifted. The same principles for
thrust on the spars or poles apply; that is, the thrust
increases drastically as the shear legs go off the
In rigging the shears, place your two spars on the
ground parallel to each other and with their butt ends
even. Next, put a large block of wood under the tops
of the legs just below the point of lashing, and place a
small block of wood between the tops at the same
point to facilitate handling of the lashing. Now,
separate the poles a distance equal to about one-third
the diameter of one pole.
As lashing material, use 18- or 21-thread small
stuff. In applying the lashing, first make a clove hitch
around one of the legs. Then, take about eight or nine
turns around both legs above the hitch, working
towards the top of the legs. Remember to wrap the
turns tightly so that the finished lashing will be
smooth and free of kinks. To apply the frapping (tight
lashings), make two or three turns around the lashing
between the legs; then, with a clove hitch, secure the
end of the line to the other leg just below the lashing
Now, cross the legs of the shears at the top, and
separate the butt ends of the two legs so that the
spread between them is equal to one-half the height of
the shears. Dig shallow holes, about 1 foot (30 cm)
deep, at the butt end of each leg. The butts of the legs
should be placed in these holes in erecting the shears.
Placing the legs in the holes will keep them from
kicking out in operations where the shears are at an
angle other than vertical.
Figure 4-39.Shear legs.