Flags are square or rectangular frames with mounting pins attached and covered with a solid cloth material. They can be used to protect the camera lens from flares or to control spill light from other sources, or to keep light from reaching certain areas on the set. Most Matthews flags use only a single, horizontally angled support arm which allows for 'close-in', right angle, tight positioning over set walls and interlocking of flags to establish a tightly controlled spread of light.