A safer was to rap should involve an Autoblock, a less clamp-like variant of the prussic knot used below the rappel device (where is doesn’t have to be an absolute clamp).

Read a Clear Description Here” It is pretty easy to follow the description offered and easy to understand how quick it is to set up.

Another link offers a picture and some good advice Note: It cautions you to consider primarily girth hitching the Autoblock loop to your harness and having the locking biner there mainly to secure the loose end. If you casually carry your Autoblock loop dangling by the biner attached to your leg loop you may drop the Autoblock loop when you open the biner to begin your wind.

Thanks, Ben!