In a self rescue situation you may have joined two ropes together with a knot, or you tied an alpine butterfly to isolate a core shot. In either case, you will need to pass a knot on the way down.
In order to rappel past a knot, you will need a cordelette in addition to your normal rappel gear (belay device and friction hitch). You will back yourself up by tying yourself to the rope below, and then use the cordelette to transfer your weight off your belay device while you re-rig the belay device past the knot.
- Rig your rappel device, and rig a friction hitch using the cordelette above your rappel device. Attach a locking carabiner to your belay loop and connect the cordelette to it with a munter mule overhand.
- Rappel until your device is about 12 inches above the knot in the rope. Guide the friction hitch with your hand as you rappel.
- Set the friction hitch so that it can grip and hold your weight.
- Back yourself up by pulling up some slack in the rope below the knot and attaching it to your harness with a locking carabiner.
- Transfer your weight onto the friction hitch and re-rig your belay device below the knot.
- Set your autoblock below the rappel device as you normally would for rappelling.
- Pull the slack through so that the belay device is as high as possible below the knot and test the new system.
- Untie the munter mule overhand carefully and ease yourself down onto the belay device (remember to hold the brake strand).
- Remove the cordelette from the rope.
- Untie your backup knot below your autoblock and continue rappelling.