Preview to: How to Pass the Knot While on Rappel (Abseil)
We isolate damaged sections of a climbing rope by tying a knot with the damaged section in the knot bight. That keeps any load - you - off of the damaged section. But if we need to rappel past a damaged section, we need to be able to get our rappel setup from above that knot to below it while staying firmly and safely connected to the rope. The full video provides a procedure to do that.
Follow this link to the full video and accompanying blog post.