CDX Plywood—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 Plywood—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.

3/4" Thick—For load-bearing applications, use ¾"-thick sheets.