The plywood is a three-layer or three sheets of sheets, which are cut into a single plate or wood, a sheet, and then glue with an adhesive. It is usually composed of an odd number, and the fibers of adjacent sheets are vertically arranged and glued to each other. Therefore, the plywood is an odd layer, such as three layers, five layers and seven layers. From the perspective of the structure, the outermost sheet of the plywood is called the surface panel, and the front surface panel is called a panel. This is the best panel with the best quality. The panel of the reverse surface is called a back plate, using a second mass of the board. The internal single plate is called a core board or an intermediate plate, composed of a panel that is the worst quality.