The term PLYWOOD SOURCE can be solved by two crossword solutions: FIR (3 letters) and BEECH (5 letters). Plywood is a type of manufactured wood panel made from thin sheets of wood veneer. It is composed of an odd number of layers of veneer, usually three, five, or seven, with the grain of adjacent layers oriented perpendicular to each other. The most common sources of wood used for plywood are FIR and BEECH.