Protect a fixed rope with a rebelay
When rigging a fixed rope, it's very important to protect the rope from being loaded over any sharp or abrasive edge.
Repeatedly loading the rope (from rappelling, and especially ascending) could damage it. Ropes often get loaded over edges on big walls, because the belay is usually on top of a ledge and not beneath it.
One way to protect your rope: the rebelay.
Rebelays have long been used by cavers, who know how to take good care of fixed ropes. Rebelays can also be useful in some climbing applications, such as big walls, instructional settings, or rescues.
A rebelay is simply adding an additional anchor(s) below the potential abrasion point. This secondary anchor can be SOLID gear you place, or a bolt.
Tie a bight knot (a butterfly works great, because it's usually easy to untie after loading) and clip it to this rebelay point.
Now, the weighted rope is on the rebelay, and not the primary anchor. All of the rope above the rebelay is slack, so it can't be damaged if it runs over an edge. Nice!
Rebelay notes and tips . . .
A rebelay can make it easier to ascend past an obstacle, such as a roof.
With a rebelay, more than one climber can be ascending or descending a rope at the same time, which can increase efficiency. (Although, for descending, this can slow things down, because you’ll probably have to pass a knot.)
When you’re rigging a rebelay, leave a bit of slack to allow for the rope to shrink. Andy Kirkpatrick says a good rule of thumb is once the rebelay is tied you want to be able to lift up about 1 meter of rope, before it comes tight on the lower anchor. (Thanks Andy! Smart tip, I never would've thought of that!)
If you’re ascending the rope rigged like the photo at the top, here's how to get past the knot.
Simply unclip your ascenders, re-clip them above the rebelay, and continue up the rope. Maintain two points of connection to the rope at all times when you pass the knot, either with a tether or a backup knot tied to your harness.
Your bodyweight is now on the rope that’s going over the edge, but now it’s only on it for (hopefully) few moves instead of the entire rope length. Much better!
If you use a tether, you can clip your tether to the butterfly loop.
If you’re the last person, you can remove the carabiner from the rebelay anchor and untie the knot.
Here's a short YouTube video I made showing how this works.