Sun board or Foam board is a very strong, light, and easily cut sheet material used for the mounting of vinyl prints, as backing in framing, and for painting. It usually has three layers — an inner layer of polystyrene foam and a white claycoated paper on the outside.
Apart from printing, Sun board is commonly used to prototype objects, produce architectural models, and to make casting patterns. Backgrounds for scale model displays, dioramas, and games (computer) are often produced by hobbyists from sun board. It’s often useful for photographers as a reflector for light in the studio, and in the design industry to display presentations of new products; Another use is with aero-modellers for building small radio-controlled aircraft.