In a situation in which one climber is incapacitated and cannot rappel by him or herself (for example, if he or she has a broken arm), then both climbers can descend together using a simple spider. The spider rappel is only an emergency technique and should never be used when any simpler rappel method is adequate. For this example we assume one climber has a minor injury that leaves him or her ambulatory but unable to rappel unassisted.
1. Both climbers are attached to the anchor with slings girth-hitched to their harnesses.
2. The rope is threaded through the anchor as in the other systems.
3. The healthy climber takes a cordelette and ties a figure eight on a bight loop in it off-center so that two loops are formed, one about twice the size of the other – this forms the spider.
4. The figure eight on a bight loop is clipped to a rappel device attached to the rope; the healthy climber clips the short loop of the spider to his or her harness with a locking carabiner and establishes his or her autoblock backup as usual.
5. The longer loop on the spider is clipped to the injured climber’s harness with a locking carabiner.
6. The healthy climber unclips his or her anchor sling, stores it, weights the rappel system, and allows the autoblock to hold them in position.
7. The injured climber’s anchor sling is unclipped from the anchor and the healthy climber assists the injured climber down until he or she is hanging off the long loop in the spider (the healthy climber can use the injured climber’s anchor as a hand line to help lower them to position); the injured climber’s anchor sling is stored once they are hanging on the spider.
8. Both climbers are now “on rappel,” each hanging from one loop of the spider (the disparity in the size of the loops separates the climbers vertically, helping to keep them from banging into each other on the way down), with the healthy climber controlling the rate of descent and backing up the system with his or her autoblock (extra wraps are advised on the autoblock because it will be holding twice the weight).
9. When the next anchor is reached, both climbers clip in with their anchor slings (on a big ledge where they both can stand, they can clip into the anchor at the figure eight loop on the spider-but the spider must be able to be slackened during the station transfer).
10. The healthy climber pulls and threads the ropes, reattaches the rappel device and the spider to the rope, and then repeats steps 6 through 10.