plywood, manufactured board composed of an odd number of thin sheets of wood glued together under pressure with grains of the successive layers at right angles. Laminated wood differs from plywood in that the grains of its sheets are parallel. Plywood is noted for its strength, durability, lightness, rigidity, and resistance to splitting and warping. It can be molded into curved or irregular forms for use in truck, airplane, and boat bodies, luggage, furniture, and tubing, or it can be made into large panels suitable for structural use. Plywood was made in ancient Egypt and China, and it was first introduced in the United States in 1865. The two types commonly in use today are those made of softwood (fir) or hardwood (birch, mahogany, walnut, or white ash). The layers in inexpensive plywood are glued together with starch pastes, animal glues, or casein, but those of the strongest plywood are glued with waterproof synthetic resins. Other material, such as metal or fabric, may be substituted for the usual wood core.
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