The most popular of these materials is a type of wood board paneling known as either beadboard or plank paneling. It's commonly used as wainscoting on walls and for the backs of Colonial-style cupboards and bookcases. These tongue-and-groove pine boards are about 5/16 in. thick x 3 1/2 in. wide and have a rounded bead milled along one edge and a second bead routed down the center. When the boards are installed, each appears to be two narrower ones. Most well-stocked lumberyards and home centers carry beadboard in 8-ft. lengths individually or in bundles. Expect to pay about $1 to $1.50 per square foot.