Made of thin layers of wood glued together under heat and pressure, plywood sheets are durable, yet lightweight. The direction of the wood grain alternates with each layer—known as opposing grain—making these sheets strong enough for building ramps and shelves or repairing holes in floors and ceilings. Opposing grains also limit movement, keeping each layer from expanding or contracting too much—otherwise moisture could warp and split these sheets apart. All are made of real wood, so you can drill, saw, sand, paint, and stain them.