Climbing descenders

Descender

— device for controlled descent on a climbing rope (the so-called rappel). Some types can also be used for insurance, including when climbing.

The general idea behind all descenders is to create more friction and thus slow down the rope slipping through the device. But the specific design and functionality of such devices nowadays are very diverse — from the simplest "eights" (a pair of metal rings) to complex mechanisms with a built-in speed control system, anti-twist protection, auto-lock when you release your hand or exceed the permissible speed ("anti-panic" mode) ) etc.