From: "James Allen"
What is the definition of the strength axis of a plywood panel?
Plywood is built up of an odd number of laminations of veneer that are
"cross-laminated". In other words, each alternating layer is oriented
perpendicular to its neighbors. When the stress is parallel to the long
direction of the panel, there are more layers that are stressed parallel to
grain and they are located farther from the neutral axis. Therefore, the
panel is stronger in this direction.