The invention relates to a device, particularly for safety braking of vehicles on rails having at least one flap unit (1) connected in a rotatable fashion to a rail, wherein the flap unit (1) may be moved into a locking position and a release position by rotation about a rotational axis (D), wherein, in a locking position, the balance point SPK of the flap unit (1) is located above a horizontal plane (E) in which the rotational axis (D) is located.