Extended Height: 6-3/4" Retracted Height: 5-1/2" Floor Truck Lock To be used with Casters having an overall height of 5 5/8" CasterHQ's Floor Truck Locks are used to hold equipment in place on level floors only. When you step on the activation pedal, a rubber pad comes in contact with the floor providing friction so that the equipment will not move. Floor Locks are not designed to lift the equipment. Install between swivel casters. Release rubber pad by stepping on either of the Release Pedals.