Drydocks, like this one at the Halifax dockyard, were especially useful in wartime when enemy action, collisions, and weather damaged many ships.

This ship, the merchant aircraft carrier MV Empire MacDermott, carried a cargo of grain in addition to operating aircraft. It would have been floated in through gates at the far end of the dock, after which the water would have been pumped out. Blocks on the bottom of the dock and braces against the dock's walls (centre right) kept the ship upright.

George Metcalf Archival Collection
CWM 19720151-033