In dry docking, a ship is removed from the water to enable work to be performed on the exterior part of the ship below the waterline. Ships are constructed on dry docks. In launching, the new or repaired ship is either floated in place or slid from its berth.
To prepare the dry dock, keel blocks are set into position and lines and men to handle the vessel are readied. A qualified dockmaster supervises the operation. Dock-based winches are usually used to position the ship in the dock.