Perpendicular placement is preferred, but KERDI-SHOWER-FRS plywood inserts may be installed with the face grain/strength axis in either direction to improve layout flexibility and reduce waste. The Engineered Wood Association guidelines for floor construction require installing plywood subfloor panels with the face grain/strength axis perpendicular to the floor joists. However, KERDI-SHOWER-FRS application testing has verified the system performance with the plywood inserts positioned with the face grain/strength axis parallel to the joists.