The Petzl Stop Descender is a belay and rappel device that was originally designed for caving where long descents on a single rope are common. It quickly caught the attention of climbers and it has since been used by all classes of climbers who need to get off the top of anything quickly, safely, and with a minimum of effort.
The Stop Descender incorporates internal cams around which the single rope runs. The rope from the top goes into the left side and around the bottom of the lower cam, then goes back upward to wrap the upper cam’s top, goes out to the right and drops towards the ground. A lever that is attached to the lower cam is on the left side.
If the handle is squeezed by your left hand, the rope is freed to feed into the cams. The speed of rope feed is controlled by the right. Varying your grip on it will either accelerate or slow the descent. If you need to stop, whether in an emergency or simply to rest, you only have to release the handle. This automatically brakes your descent.
Inserting the ropes into the Stop Descender does not require you to remove it from your harness. It has a spring clip allowing one side of the frame to pivot on an axle to expose the internal cams.
The Stop works with ropes with a diameter of from 9 to 12 millimeters. Dry, clean, and flexible ropes are most suited for this descender. Stiff and wet ropes may not be sufficiently gripped by the cams, thus endangering your descent.