Displacement and locking device for two assemblies and transport vehicle with such a device

First (22) and second (26) counter-bearing elements (CBEs) fasten on a first modular unit (MU) (12) with a clearance (A). A shift device (SD) (32) triggered by a control device (18) has a linear unit (36) to shift lengthwise in a bearing unit (34) and fastens on a second MU (14). When both MUs are set up, the SD fits between first and second CBEs.