clapboard, type of board bevelled toward one edge, used to clad the exterior of a frame building. Clapboards are attached horizontally, each one overlapping the next one down. They are six to eight inches in width, diminishing from about a 5/8 inch thickness at the lower edge to a fine upper edge which is under the board above.
Cleft oak clapboard was introduced to New England in the 17th century. Later clapboard was generally made of pine, cypress, or cedar. Clapboards are applied with about four inches exposed. A device called a clapboard gauge may be used for spacing and to keep them parallel.