It is used in vessels of all sizes along the coast of the United States a retractable fin keel used on sailboats to prevent drifting to leeward
A movable or sliding keel formed of a broad board or slab of wood or metal which may be raised into a water-tight case amidships, when in shallow water, or may be lowered to increase the area of lateral resistance and prevent leeway when the vessel is beating to windward