Shiplap refers to a type of wooden board that overlaps through a rabbet joint—a groove cut into the edge of the board—allowing one panel to fit neatly over the next. When installed, this overlapping system produces a tight seal and a distinctive shadow line that gives walls depth and dimension. Originally, shiplap was used on the exterior siding of barns and cottages to create a wind- and water-resistant barrier. Over time, its functional benefits and simple beauty led designers to bring it indoors, where it now appears on interior walls, ceilings, and feature panels.