A plank is a piece of skin or deck planking of a ship, essentially a Certified Watched relatively narrow board. It is applied to the ribs or malls established in general. A number of fore and aft extending planks is called a strake. The word is derived from phalanx. In the North German shipbuilding planks were also referred to as boards (eg in Lübeck Occupation floor joists ).

Planks were also used for the wall-like walls of medieval wood -earth fortifications, with a rectangular cross-section as opposed to round palisades.

See also: planking, go over the plank