Stand the plywood underlayment panel vertically with its 4' edge on the floor and the panel face towards you (For SurePly® plywood and IronPly® plywood, the staple/nail pattern will be facing you. For RevolutionPly® plywood, the stickers are on the back of the panel).
Grip the top of the panel edge with one hand and firmly place the palm of your other hand against the face of the panel.
Pull the panel down approximately 4”-8" with your top hand while simultaneously pressing forward with the palm of your other hand approximately 4”-8" until a noticeable curve is in the panel. Hold this position during inspection.
With the plywood underlayment panel in this flexed position, thoroughly inspect the entire panel surface for imperfections, which will look like "bubbles" or "creases." In the rare instance you find such an imperfection, do not use the panel. Set it aside, and contact Patriot Timber Products immediately for a resolution.