This method is used for clean rappeling anchors and avoids leaving any webbing/slings behind. In some areas, leaving rap anchors is illegal. It is always a good idea to leave as little behind as possible.
This method can be modified for pitons/bolted anchors as well. This is just for fun and clean climbing ethics most of the time. No one has to use the method.
Photo 1: Runner is tied with rap rings and set around anchor. Pull cord is tied to sling.
Close up of Photo 1
Close Up Photo:
Photo 2: Rope threaded through rap rings.
Photo 3: Rappel down.
Photo 4: Pull climbing rope. Notice that the sling and pull cord are not attached to the climbing rope and in no way effect it from the "standard" method of rapping. (Note: In a real-life situation, it is better to have the ringbend/water knot of the sling/runnder on the same side as teh pull cord. For the photos, I put it on the opposite side so you could see the knots better, and to emphasize that the pull cord in no way is affects the climbing rope, or water knot.)
Photo 5: To retreive sling, simply pull the "pull cord". If it ever did get stuck, the only thing you would loose is the pull cord, never the climbing rope, hence no extra risk.
Photo 6: Sling comes down, ready for the next rap. Using this, no more tying required for rest of descent.