CMI Rigging Block for 1/2 in Rope

The CMI rigging block for 1/2 inch rope is a pulley block used to redirect the line from the piece to a lowering device at the base. Using a block instead of a natural crotch reduces friction on the tree and wear on the rope.

How the block is used

Hang the block from a sling choked or girth-hitched around a sound anchor above the work. The rigging line runs through the sheave down to a lowering device at the base, where the ground worker controls the descent. Because the sheave turns, the line runs freely and the ground worker gets consistent, predictable friction from the device.

Remember that the block and anchor see roughly double the load on the rope, since the line pulls from both sides. Choose a sling and anchor that can handle that, and keep drops short to limit shock loads.

A small block is easy to carry up on the saddle, so you can set it as you go rather than sending it up on a line. That makes it a good fit for pruning jobs where you lower a handful of limbs over a roof, garden, or fence, then move on to the next tree.

Inspection

Before each use, check the side plates for cracks or bending, confirm the sheave spins smoothly without wobble, and look for grooves worn by rope. Use only rope within the block's listed diameter. See larger options in our rigging blocks section.

Rigging forces are dynamic and can be several times the weight of the piece. Follow the manufacturer's ratings and ANSI Z133, inspect every component before the job, and keep rigging work to trained crews.