Barndoors are an essential accessory for any lighting system. This device alters the shape of the light output from your fixture. Use of a barndoor set will result in a controlled beam of light, when it is attached to the front of the fixture housing of your light source. The shape of the light beam will be determined by the opening of the leaves, and the distance of the light from the scenery. Barndoors are also useful when trying to keep lighting from hitting specifics areas. 4-leaf barndoors provide more light control than 2-leaf barndoors.