Vessels having boards, plates, planks, etc., placed longitudinally amidships and projecting in line with the keel or approximate thereto and adapted to be raised or lowered to increase the resistance-surface and prevent capsizing or sudden careening, thereby steadying and trimming the vessel, usually preventing making to leeward, and enabling a vessel to point or sail closer to the wind. Centerboards are usually short in length and move in a recess or casing formed in the bottom of the vessel and raised, lowered, or adjusted at will.
