The device (2), which is used to lock running gear (1) guided in a rail (5) and is or can be connected to the latter, has a body (21, 22) in which a locking pin (23) is displaceably mounted and, by means of a resilient element (24), is held resiliently in a first position, so that the locking pin (23) can be brought by the action of a force from the first position, in which it can engage in a locking element (36, 53) provided in the rail (5) or connected to the rail (5), into a second position, in which it is released from the engagement in the locking element (36, 53). The locking device (2), which is constructed simply and cost-effectively, therefore permits dividing elements (90), such as sliding doors, sliding counters or folding walls, which are guided by the running gear (1), to be closed off securely.