Descenders allow a controlled descent of a rope to access a work position or for emergency evacuation or rescue. For rope access, rigging or rescue use, a self-locking descender (one which stops the descent if the user lets go) should be chosen. In addition, rope diameter, rated load and other locking features should also be considered.
Belay devices control the passage of the rope when lead climbing. Most are not self-locking and should be used with caution in work applications