Each layer, or ply, is peeled from a log and so arranged that the grain will run at right angles to that of the layer above and below it. This keeps the wood from warping and splitting. The plies are glued together under pressure, either in a wet or dry state. Dry plies make a better plywood as the tendency toward shrinkage is reduced.
Varieties of plywood called laminated and batten are made by having the veneers lie perpendicular to the outside layer. Plywood is always made with an odd number of veneers, as 3 ply, 5 ply, etc.
Plywood is used where large, lightweight, strong panels are desired as in walls, doors, furniture, railroad cars, boats and boxes.
If properly glued, plywood is very weatherproof.
