Abstract: Apparatus for securing a wheelchair to the floor of a vehicle or the like comprises two pairs of clamp posts journaled for up and down movement. Each post has a pair of clamp jaw members positioned to engage the wheelchair underframe. A main piston raises and lowers the posts simultaneously. Each post has a pair of clamp jaw pistons operatively connected to the corresponding clamp jaw members to grip the underframe. A control circuit comprises an electrical-motor-operated pump, a four-way solenoid-operated direction control spool valve, a pair of sequence valves, pilot operated check valves in the pressure lines leading to the clamp jaw pistons, and a three-way electrical toggle switch having "UP", "DOWN" and "OFF" modes. In "UP" mode the main piston lifts the clamp posts to and optionally beyond a position to engage the frame where one of the sequence valves directs pressure fluid to the clamp jaw pistons to lock the clamp jaws onto the frame.