origin. The most popular standards are the British Standard (BS) and the American Standard (ASTM). Joyce (1970), however, list some general indication of grading rules: Applications Plywood is used in many applications that need high-quality, high-strength sheet material. Quality in this context means resistance to cracking, breaking, shrinkage, twisting and warping. Exterior glued plywood is suitable for outdoor use, but because moisture affects the strength of wood, optimal performance is achieved where the moisture content remains relatively low. Subzero conditions do not affect the dimensional or strength properties of plywood, making some special applications possible. Plywood is also used as an engineering material for stressed-skin applications. It has been used for marine and aviation applications since WWII. Most notable is the British de Havilland Mosquito bomber, with a fuselage made of birch plywood sandwiching a balsa core, and using plywood extensively for the wings. Plywood was also used for the hulls in the hard-chine Motor Torpedo Boats (MTB) and Motor Gun Boats (MGB) built by the British Power Boat Company and Vosper's, American PT boats, and the Higgins landing craft critical to the D-Day landings. The American designers Charles and Ray Eames are known for their plywood-based furniture, as is Finnish Architect Alvar Aalto and his firm Artek, while Phil Bolger has designed a wide range of boats built primarily of plywood. Jack Köper of Cape Town designed the plywood Dabchick sailing dinghy, which is still sailed by large numbers of teenagers. Plywood is often used to create curved surfaces because it can easily bend with the grain. Skateboard ramps often utilize plywood as the top smooth surface over bent curves to create transition that can simulate the shapes of ocean waves. Softwood plywood Typical end uses of spruce plywood are: Floors, walls, and roofs in home constructions Wind bracing panels Vehicle internal body work Packages and boxes Fencing There are coating solutions available that mask the prominent grain structure of spruce plywood. For these coated plywoods there are some end uses where reasonable strength is needed but the lightness of spruce is a benefit, e.g.: Concrete shuttering panels Ready-to-paint surfaces for constructions Hardwood plywood Phenolic resin film coated (Film Faced) hardwood plywood is typically used as a ready-to-install component e.g.: Panels in concrete form work systems Floors, walls and roofs in transport vehicles Container floors Floors subjected to heavy wear in various buildings and factories Scaffolding materials ("Wire" or