Ships Cover for the Department of Naval Construction's development of a proposal for a concrete fort to interdict the ports of Zeebrugge and Ostende. Known as the 'MN' scheme, these structures were designed to be towed into position and sunk in place. Various designs were produced and armament ranged from 6-inch to 15-inch guns. The idea was not implemented as it was rendered unnecessary by the Zeebrugge and Ostend raids of 1918 and the subsequent advances of the British Army rendered these ports untenable as U-boat bases. However, one structure on a smaller scale was completed and deployed in 1920 as the Nab Tower. The papers cover the period May 1917 to July 1919.