The two upright arms of the frame are slotted at the two open ends to retain the piano wire woven through the fabric to make up the fourth side of the frame without causing a shadow. Open Ends are used to control or manipulate light falling on certain areas of the set or subject. They can be used to soften or reduce light without a noticeable edge. A colour coded binding is used around the frame to identify the fabric. Matthews Open End Frames are black powder coated to minimize unwanted reflections.