Derek Hansen

“Descender Rings—These small metal rings are also borrowed from the climbing and rappelling community. Originally used to facilitate the recovery of rope on a rappel, you can use two descender rings together to adjust the length of long webbing between tree and hammock. Weave the webbing strap through both rings and then back through the top one. Descender rings require a safety knot (half hitch) to prevent the webbing from slipping.”
― Derek Hansen, The Ultimate Hang