Mounting unit for a trailer

The construction unit (4), especially of the trailer of a lorry, has a floor (4.1) and sliding wall (4.2). The drive mechanism (4.3) of the sliding wall has at least one fixed drive train and a rotating drive element mounted on the wall. A recess which is open at the top is formed in the floor region to house the drive train, and means are provided in the floor region to cover the recess. The drive train is located in the region of the longitudinal center plane of the construction unit. An independent claim is included for a vehicle, especially a trailer, with the aforesaid construction unit.