A torsion box consists of two skins to carry the applied loads on either side of a core material usually constructed as a lightweight grid of thin beams. A hollow core door is probably the most commonly found example of a torsion box (stressed skin) structure. Like an I beam or truss, the idea is to use less material more efficiently. The torsion box uses the properties of its thin surfaces to carry the imposed loads primarily through tension and compensate for the tendency of the opposite side to buckle under compression by placing the web material grid closely spaced to reduce the span of the material. In part, the flat surfaces also carry the load by resisting being deformed into a complex curve just as a curved egg shell resist being flatten. Torsion boxes are also used in the construction of structural insulated panels for houses, airframes, especially wings and vertical stabilizers, in making wooden tables and doors, and for skis and snowboards.