An apparatus is disclosed for mutually locking two switches, in particular circuit breakers, with two plungers which move in opposition to one another via a forced mechanical coupling. When one switch opens, one plunger is shifted into its opening position and the other plunger is shifted into its locking position. In order to achieve a maintenance-free apparatus, at least one embodiment of the invention proposes that each plunger has a toothed rack, which meshes with a gearwheel, on which in each case one radial lever is arranged. The levers are connected in articulated fashion to one another via a connecting rod and a stop lever is mounted in rotary fashion on each gearwheel and, when the plungers are located in the zero position, bears in each case against a fixing stop. Furthermore, a driver is located on each gearwheel and bears in each case against a stop face formed on the stop lever, wherein, when a plunger is shifted, in particular when a switch opens, one driver pivots the stop lever towards a spring, while the other driver is removed from the stop face of the stop lever.