Plywood

Plywood is a material manufactured from thin layers of timber called veneers, they are glued together with adjacent veneer layers rotated up to 90 degrees to one another. The veneers are then layered and bound by resin and cold or hot pressed (dependent on plywood type) to create the desired thickness of the material.

Alternation of the grain is called cross-graining and has several important benefits: it reduces the tendency of wood to split when nailed at the edges; it reduces expansion and shrinkage, providing improved dimensional stability; and it makes the strength of the panel consistent across all directions.

There is usually an odd number of veneers, so that the sheet is balanced—this reduces warping. Because plywood is bonded with grains running against one another and with an odd number of veneer layers, it has high stiffness perpendicular to the grain direction of the surface ply.