Descenders Professional devices are usually used on single ropes and often have an automatic braking or blocking function. Releasing the brake initiates the abseiling process; when the brake is released, the device brakes automatically. Depending on the type, abseiling devices can also be used for belaying during lead climbing. In addition to the purpose of abseiling or belaying, the choice of the correct rope ("dynamic" for belaying, "semi-static" for abseiling) and the correct rope diameter for the device must be taken into account. Pure rescue devices are sometimes equipped with a lifting function and have a defined maximum abseiling speed and are offered with a fixed rope in various lengths. Devices according to EN 12841 type C are intended for work on the rope as well as for rescue, devices according to EN 341 are approved as evacuation and rescue devices, often both standards are applied.