Plywood has an odd no. of layers so that this is at right angles for strength inside but runs the same way outside
There is usually an odd number of plies, so that the sheet is 
balancedthis ... below and right) may only have their plies (layers) arranged at 
right angles to .... High-strength plywood also known as aircraft plywood, is made 
from... [DOC] [TLE] bvr plywood - sstraders [PAR] Plywood is a sheet material manufactured from thin layers or "plies" of wood 
veneer that ...