86  RIGGING, HOISTING, and SIGNALING PRACTICES
While most loads are hoisted in a horizontal orientation, some require hoisting in a vertical orientation, which presents additional difficulties. Approved belowthe-hook devices, such as clamps, can be temporarily added to the load as mechanical stops. These stop the sling from shifting position or sliding off a vertical load. Choker hitches can cause significant wear on the inside of the eye where it contacts the sling body, particularly for wire rope slings. To prevent this damage, a shackle can be used in the lower eye to form the choke. See Figure 6-13. A shackle would resist wear longer than the sling eye would and is easier to replace when necessary. A shackle should be connected with the pin inside the sling eye so that pulling on the body of the sling does not cause the pin to unscrew.
Bridle Hitches
Shackles in Choker Hitches POINT OF SIGNIFICANT WEAR PIN IN SLING EYE
SHACKLE
WIRE ROPE SLING
Figure 6-14. A bridle hitch is formed from multiple slings that are attached to the load at one end and gathered together at the other end, forming a triangle shape. Some rigging assemblies include multiple bridle hitches.
Figure 6-13. Shackles can be used to form choker hitches so that a sling eye does not wear prematurely.
Bridle Hitches A bridle hitch allows a load to be secured at more than one point, which increases load stability and allows greater control of the load. See Figure 6-14. Most bridle hitches consist of a group of slings connected to attachment points on a load similar to vertical hitches, except at an angle. The tops of the slings are gathered at a common hook or fitting. However, bridle hitches can also consist of a group of choker hitches and basket hitches. They become a bridle hitch because they are similarly joined at the top. A bridle hitch is rigged with a bridle sling. A bridle sling is an assembly of two or more sling legs, each with an end gathered together at a common end fitting. Bridle slings may be purchased as a prefabricated assembly or assembled in the field from individual slings.
A choker hook is used to quickly form a choker hitch on a wire rope without having to thread one end of the sling through the other end’s eye.