The first step to tie an autoblock knot is to clip a carabiner, preferably a locking one, onto the leg loop of your harness. Clip it on the side where your brake hand will be.
First, wrap the cord or sling several times around the rappel rope.
Wrap the Cord Around the Rope
Next wrap your autoblock cord four or five times around the rappel ropes.
More Wraps Equal More Friction
Use up most of the cord on the wraps. How many wraps you put on is up to you, but the more wraps, the more friction. If you don’t use enough wraps, the autoblock will slip on the ropes, particularly if they are new and slippery. If you use too many wraps, the knot won’t slide easily. Make sure that the cord’s knot or the sewn overlap on the sling are not in the knot itself on the rope, but rather on the outside of the knot as in the photograph above.
