The main part of this lid is made of tongue-and-groove. The end cleats fasten these together in a 1/4" deep groove with 1 3/4" for a skirt and 1/2" above. Another piece fastens flat-wise on top. This piece also has a 1/4" thick lip to come out over the skirt pieces. This eliminates the crack that allow water into the ends of the tongue-and-groove pieces. We recommend using long nailsor 2" staples through that 1/4" lip and down through the end to bind it all togetherso that the skirts do not break off so quickly. Aluminum for the center area is available.