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.

The two side walls were folded down under tow to reduce wind resistance and lower the center of gravity.

[1][2][3] The ABSD-4 floating drydock departed California in 1944 and made the voyage across the Pacific Ocean in convoys in 48 days.

ABSD-4 had provisions for the repair crew, such bunk beds, meals, and laundry.

[4][2][5] [6] [7][3] Some of the ships repaired: Near the end of the war on April 22, 1945 at 2pm a Mitsubishi A6M Zero two seater plane piloted by Shimbo and Ensign Chuhei Okubo in the second seat, overflew Seeadler Harbor at 14,000 feet.

They saw what they thought were two "aircraft carriers", but here actually empty floating dry docks ABSD-4 and ABSD-2.

On April 27, 1945 at about 11:15pm a three Nakajima B5N a Japanese Zero fighter aircraft of the Imperial Japanese Navy flying from Truk flew over ABSD-4, one plane dropped an aerial torpedo and it hit one of the pontoons tanks of ABSD-4 damaging the dry dock.