A damaged rope can be totally useless for doing most tasks safely, especially if the damaged section is somewhere in the middle. This simple knot can bypass the damaged section and make the rope fairly safe to use again. This video lesson from Bryan Black at ITS Tactical explains how tie the leg bone-looking sheepshank knot. Find the damaged section of rope, then make a loop with the damaged section at the top of the loop. Make two more loops in the rope with one on either side so the damaged loop is in the middle. Then pull the middle damaged loop through the loops on either side until it's tight. Once it's tied, the knot will take the weight off of the damaged section of rope so it doesn't get damaged further and snap. Black notes, however, that you should never use damaged rope if it will be bearing somebody's weight, and that this technique should only be used when absolutely necessary. If you're able to easily replace your rope, just do that instead.