Plywood is a type of manufactured timber made from thin sheets of wood veneer. It is one of the most widely used wood products. It is flexible, cheap, workable, recyclable, and can usually be locally manufactured. Plywood is used instead of plain wood because of its resistance to cracking, shrinkage, and twisting/warping, and its general high degree of strength.
Plywood layers (called veneers) are glued together with adjacent plies having their grain at right angles to each other for greater strength. There are usually an odd number of plies so that the sheet is balanced—this prevents warping. Because of the way plywood is bonded (with grains running against one another and with an odd number of composite parts) it is very hard to bend it perpendicular to the grain direction.
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