Shiplap is crafted with a rabbet or notch cut on both edges of the board. Like the tongue and groove of generic wooden planks, this shape allows for cladding, which is a technique in which one material is placed over the other. When these boards are installed horizontally or vertically, they will naturally slide and “lap” one on top of the other, creating a perfect fit as they self-space. The finished product will be flush and solid with a tight seal.