A belay device is a mechanical piece of climbing equipment used to control a rope during belaying. It is designed to improve belay safety for the climber by allowing the belayer to manage their duties with minimal physical effort. With the right belay device, a small, weak climber can easily arrest the fall of a much heavier partner. Belay devices act as a friction brake, so that when a climber falls with any slack in the rope, the fall is brought to a stop.
Petzl Reverso, Verso, GRIGRI
Sticht plate.
A figure-eight descender.
Petzl Reverso
In climbing and mountaineering, the term belaying refers to techniques used to create friction within a climbing protection system, particularly on a climbing rope, so that a falling climber does not fall very far. A climbing partner typically applies tension at the other end of the rope whenever the climber is not moving, and removes the tension from the rope whenever the climber needs more rope to continue climbing. The belay is the place where the belayer is anchored, which is typically on the ground, or on ledge but may also be a hanging belay where the belayer themself is suspended from an anchor in the rock on a multi-pitch climb.
A demonstration of the belay device with rope and carabiner without a proper locking gate
Belay device held in the "locked off" position.
Leader and belayer climbing in Joshua Tree National Park
Lead climber and belayer (in a hanging belay position) on the multi-pitch El Niño 8b (5.13d), El Capitan