The seat (1) has a lower frame (2) supporting the platform (3) which can be raised vertically relative to the lower frame and is lockable thereon. The lower frame comprises two or more telescopically movable lockable frame parts. The vertical adjustment is through a cable pulley or threaded spindle or gearwheel system with manual or motor operated drive. A hydraulically operable piston cylinder unit can be used. The locking means can be swivel or tip-up locking bodies (26) which are pretensioned in the locking direction by gravity or spring force. On reaching the upwardly extended position the platform and/or movable frame part automatically pass into the locked position. The seat can be designed as a trailer or as a self-drive vehicle.
