Plywood is a manufactured wood product that is made from multiple layers or plies of thin solid wood that are glued together to form a panel of a specific thickness. The plies are oriented so that the grain direction in one ply is rotated 90° relative to adjacent plies. This enhances both the strength and dimensional stability of the plywood. There is usually an odd number of plies in a sheet of plywood.
Plywood is most commonly sold in thicknesses ranging from approximately 3/16 to 3/4 of an inch. A standard sheet of plywood measures 4 feet wide by 8 feet long, although 4' x 8' oversized plywood, can also be custom ordered.
Plywood is made from both softwoods and hardwoods and is available in a number of grades based on the quality of the face and back veneers. For example, A grade plywood is practically free from all defects in the face and back veneers whereas X grade plywood has plenty of knots, knotholes, cracks and other defects