Screw-dock.
(Hydraulic Engineering.) A contrivance for lifting a vessel out of the water, in order that the bottom may be examined and cleaned. The vessel to be raised by this apparatus is floated over a platform of wood, sunk to the depth of about 10 feet below the surface of the water, and suspended from a strongly built wooden framework by iron screws from 4 1/2 to 5 inches in diameter. This platform has several shores on its surface, which are brought to bear equally on the vessel's bottom, to prevent her from heeling over on being raised out of the water. The platform is gradually raised to the surface of the water, carrying the vessel high and dry, suspended between the wooden frames.