Most commercial and contest ramps are surfaced by attaching sheets of some form of masonite to a frame. Many private ramps are surfaced in the same manner but may use plywood instead of masonite as surface material. Some ramps are constructed by spot-welding sheet metal to the frame, resulting in a fastener-free surface. Recent developments in technology have produced various versions of improved masonite substances such as Skatelite, RampArmor, and HARD-Nox. These ramp surfaces are far more expensive than traditional materials.