CDX plywood is a type of plywood that is made by bonding at least three layers of wood together, and the finished product ultimately features a different grade of plywood veneer on either side, one C-rated piece and one D-rated piece. The letters C and D represent the grades of either side of the plywood, while X stands for exposure. The X in CDX refers to the type of glue used in the factory to bond the plywood veneers. CDX is known for its strong resistance to cracking, breaking, or twisting. It is a lower grade plywood with the most number of knots and defects. CDX plywood is commonly used for exterior applications such as roof sheathing, construction of crates and boxes, and as a sub-floor to ceramic floor finishings like in kitchens and bathrooms. It is also used for minor utility purposes, such as rudimentary shelving in basements, storage cabinets, or sheds. However, because of its low-quality exterior, CDX plywood is not often used for pieces of furniture that require a more finished appearance inside the home. CDX plywood is not waterproof, but it is water-resistant and can withstand a little moisture.