Petzl Stop
A Petzl Stop is a descender[1] used primarily in caving and industrial rope access made by the French company Petzl.
Usage
The Stop is for use with single ropes between 9 and 12 mm in diameter and is usually attached to the harness via a carabiner. The rope is then threaded through the cam and bobbin by undoing the safety clip and moving the swinging side plate to the side. The swinging side plate facilitates insertion and removal of the rope without the need to disconnect it from the harness, making it less likely to be dropped on long abseils.[1] As the Stop is a self-braking descender, an unintentional release of the deadman's handle should stop the descent, due to the asymmetric lower cam crimping the rope. This functionality safeguards the user in the event of being knocked unconscious due to a rockfall or illness, though the fine control of rate of descent should be carried out by standard method of manually controlling friction with the hand on the rope below the descender.
Standards
References
http://www.taylorstreeservices.co.uk/