The fundamentals of anchoring are covered in many more places, but there are a few things to consider when an anchor will be used for a rappel. If the anchor is fixed (for example, two bolts with a chain and lap link or ring), then all you need to do is thread the rope and go. With all anchors, be absolutely certain that the rope will not rub against any potentially dangerous edges during the rappel, ropes under tension cut very easily!
If the anchor is one you have built yourself, it must be SECURE. For rappelling, the anchor should ideally be situated high enough so the rappeller does not have to make an awkward transition over the cliff edge or off the ledge before he or she begins the descent.
The ideal rappel anchor enables the person rappelling to assume the correct body position and put his or her weight on the rope before going over the edge. If this is not possible, a separate belay rope can be used to help ensure safety and maintain control while the rappeller is making the transition over the edge.
Trees are commonly used as rappel anchors.
They are usually very strong and, if they are big enough, the anchor can be constructed high on their trunks, which makes the transition over the edge easier.
However, trees-even big ones-should be treated carefully. If climbing ropes are frequently wrapped directly around the tree and then weighted, the resulting wear will damage the bark and, if done often enough, can even kill the tree. Pulling the rope around the tree can also damage the rope-heat builds up and can melt the sheath. In order to keep trees healthy (and thus extend their life as bombproof anchors), try to always do the following:
- Whenever possible, wrap the tree using a sling and carabiners to create your anchor.
- If the tree will be used frequently for rappelling, consider creating a semipermanent anchor with slings and rappel rings (semipermanent because the slings will need to be replaced occasionally).
- If you must wrap the rope directly around the tree, pull the rope very slowly after the rappel to minimize friction damage to the bark or the rope.
It is common when rappelling multi-pitch routes to find rappel anchors consisting of multiple slings around trees or through fixed anchors such as pitons. Do not assume that just because there is a lot of webbing, the anchor is reliable. Check each individual anchor, and do not rappel until you are satisfied that it is strong enough. Be wary of the “American Triangle,” which consists of a sling or slings tied through two anchors (pitons or bolts), forming a triangle. This configuration needlessly increases the stress on each anchor point.
Additionally, fixed sling anchors often are not equipped with rappel rings, meaning that parties before you might have wrapped their rope around the slings themselves. Check the slings for wear at the point where the ropes might have been rubbing on them.
Frayed or melted slings should not be trusted. The best thing that you can do in situations like this is to cut away any slings that appear old or arc damaged, replace them by tying new slings to each anchor separately, threading rappel rings into the loops tied into the ends of the slings at the master point. You now have created a safer anchor with less stress on the individual anchor points, and a durable master point to run the rope through.