Abstract: A rack (16) extends along a support column (12) for a work platform (10) which is guided for up and down movement along the support column (12). A pair of independently movable supports (32, 34) are provided. A separate extendible/retractable hydraulic cylinder (64, 68) is interconnected between each support (32, 34) and a frame portion (30, 88, 90) of the work platform (10). Each support (32, 34) includes an extendible/retractable lock element (100) having an end portion which when the lock element (100) is extended is in locking engagement with either tooth portions of a pinion wheel (56) carried by the support (32, 34), or with the rack (16). In use, the lock element (100) is extended to lock the support in position relative to the support column (12). At the same time, the hydraulic cylinder (64, 68) which is connected to the support (32 or 34) is extended or retracted to raise or lower the work platform ( 10).