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. For load-bearing applications, use 3/4"-thick sheets. 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.

CDX-grade plywood sheets are best for applications that will be painted or covered by another material. They can be briefly exposed to moisture, such as during construction, but shouldn't be exposed long term. One side is C-grade, so it may have minor surface defects and knots. The other side is D-grade, which may have more defects and bigger knots.

Marine-grade plywood sheets meet BS 1088, an international standard for plywood made from water- and fungus-resistant hardwood. Often used to make boats, their layers are bonded with waterproof glue, so they won’t bubble, buckle, or delaminate with long-term exposure to weather and water. Boiling temperatures and steam aren’t a problem either. Compared to CDX plywood sheets with the same thickness, these sheets have thinner layers and more of them, making this plywood stronger and denser. Each layer is made from one piece of wood, so there are no gaps in the middle layers that could weaken the sheet or leave a rough edge when you cut or sand it. The outer layers have a finished appearance that doesn’t need to be painted.