CDX plywood sheathing is a type of plywood veneer that is resistant to moisture. The "X" in the name stands for "exposure." CDX plywood is not waterproof, however, and cannot withstand significant moisture for a prolonged period of time.
CDX plywood sheathing is also renowned for its structural integrity and strength, and it finds extensive use in outdoor construction. It is used in many different types of construction jobs because of its resistance to puncture damage, impact and splitting. This last quality means it can be nailed and stapled near the edges of paneling jobs without risk of breakage at the seams.