USS ABSD-4, later redesignated as AFDB-4, was a nine-section, non-self-propelled, large auxiliary floating drydock of the US Navy. Advance Base Sectional Dock-4 (Auxiliary Floating Dock Big-4) was constructed in sections during 1942 and 1943 by the Mare Island Naval Shipyard in Vallejo, California for World War II. With all ten sections joined, she was 927 feet long, 28 feet tall (keel to welldeck), and with an inside clear width of 133 feet 7 inches. ABSD-4 had a traveling 15-ton capacity crane with an 85-foot radius and two or more support barges. The two side walls were folded down under tow to reduce wind resistance and lower the center of gravity. ABSD-4 had 6 capstans for pulling, each rated at 24,000 lbf (110,000 N) at 30 ft/min (0.15 m/s), 4 of the capstans were reversible. There w