A vehicle restraint restrains a vehicle at a loading dock by engaging a rail that is part of the vehicle's support frame, wherein the rail is normally used for adjusting the position of the vehicle's rear wheels. In a preferred embodiment, the restraint includes an adjustable-length arm attachable between the vehicle and the loading dock. The arm includes a retractable or removable pin that engages one of a series of holes in the rail or releasably engages some feature of the loading dock. In some examples, the restraint clamps onto the rail, particularly if the rail has no available open holes for a pin to be inserted. In some cases, the restraint also provides the vehicle with vertical support.