Shane S wrote:Not all the fig 8's have a tie off bar. If not a complete overhand knot should suffice. Make sure it's a complete overhand and not a half hitch "often confused".
I disagree with the advice above. It is the exact opposite of what I was recommending.
If you tie an overhand, when you weight the eight for the rappel test the knot can seize and become impossible to untie. (ask me how I know this
) It is the only thing holding your weight, besides a tiny bit of friction on the eight. It is often necessary to go onto ascenders to release the overhand, and then you have to start over. Even if you were able to untie the incredibly weighted knot, if you use two hands to do it, then you end up releasing the rappel device with no hand on the brake. This is generally not a good idea.
If you instead tie a half-hitch on a bight just above the rappel device, that is called a mule knot, recommended above by P. Fitzgerald Johnson. The mule will butt up against the rappel device and stop you from moving downwards. (soft-lock)
Once you have the mule tied, THEN tie it off with an overhand. This gives you a hard and soft lock. To unlock, untie the overhand (hard lock) and get a grip on the rope below the rappel device. The real beauty of the mule knot IMO is that when you pull the mule loop through, it releases the soft lock, AND you end up with the brake end of the rope in your brake hand ready to rappel.