This extra man is responsible for feeding you rope and lowering you as you descend your route, using a friction device such as an ATC or Gri-Gri to do so. You’ll also observe in a number of recreational facilities (such as River Rock) something called an auto-belay a device that acts as an anchor at the top of the route and serves to catch you if you fall. In the end, top-roping is a great way for beginners to get used to rock-climbing, but it can also be a preferred way for veterans to learn and practice a new route.
