The Petzl Stop was originally designed for cavers, the idea being that the handle/ trigger is depressed to commence the descent and works as a brake or a ‘dead man’s handle’ if you let it go. Unfortunately, the system is not perfect and a few accidents have occurred when the handle got caught, allowing a free fall, and it can ‘creep’ in the locked position necessitating an extra lock off by wrapping the rope around the whole device. The Industrial Rope Access Industry (I.R.A.T.A.) use them a lot, though often prefer the Petzl I.D or a Gri- Gri. Stops seem to have been around since the 1980s and this particular one was once used by Mick Tighe for Mountain Rescue Training.