Abstract: A composite structure having a coating of thermoplastic material on a substantially inflexible substrate is disclosed. The composite structure comprises (a) a substantially inflexible substrate having a plurality of orifices in the surfaces thereof that is coated, the orifices being of a shape such that, at least in part, the cross-sectional area of the orifices increases as the distance from the surface of the substrate increases, and (b) a coating of solid thermoplastic material on the surface of the substrate. The thermoplastic material extends into the orifices at least as far as into the portion of the orifice of increasing cross-sectional area. Preferably the cross-sectional area of the orifices is greater than 0.005 square inches and the thickness of the coating is at least 10 mils. The substrate is preferably a cellulosic material, e.g., wood, hardboard plywood and the like, or metal. The thermoplastic material may be asphalt, bitumen, tar or a thermoplastic polymer, especially polyethylene.