An Auxiliary repair dock (ARD) is a type of floating drydock employed by the U.S. Navy, especially during World War II. The Navy commissioned 33 ARD vessels: ARD-1 through ARD-33. ARDs were self-sustaining in World War II. ARDs have a rudder to help in tow moving, making ARDs very mobile, and have a bow to cut through waves. ARDs have a stern that can be opened or closed. The stern can be closed with bottom-hinged flap gate, operated by hydraulic rams. This stern gate can be lowered for ship entrance into the submerged dock, and then closed to keep out waves. ARDs were built by the Pacific Bridge Company, in Alameda, California.