A 4 ft. x 8 ft. x 5/8 in. CD plywood panel is a versatile building material commonly used in construction and woodworking projects. The "CD" grading indicates that one face of the panel has a "C" grade, which may have visible knots and defects, while the opposite face has a "D" grade, with more noticeable imperfections. This type of plywood is typically used for structural applications where appearance is not a primary concern.