An A-frame is a basic structure designed to bear a load in a lightweight economical manner. The simplest form of an A-frame is two similarly sized beams, arranged in a 45-degree or less angle, attached at the top. These materials are often wooden or steel beams attached at the top by rope, welding, gluing, or riveting.
Because they have only two "legs", A-frames are usually set up in rows so that they can have good stability. A saw horse is a good example of this structure. More complex structures will have a crossmember connecting the two materials in the middle to prevent the legs from bowing outwards under load, giving the structure the appearance of the capital letter A.