Abstract: A movable fall-preventing device (1) for a belay support (6) includes an axis-retaining groove which retains the belay support (6) by means of a lever (16) that pivots between an open position and a closed position. One end of the lever comprises a locking cam and the other end is provided with a hole intended to receive a snap hook (5). An end stop system limits the pivoting movement of the lever (16) in an intermediary position when switching from the closed position to the open position. The end stop system comprises a retractable, movable stop (50).