vertical or horizontal structure typically made of wood, metal, or plastic divides panels or sections of a window, door, or partition usually has a frame around the edges wide and thin, usually with a uniform width can be decorative or plain
mullion which has vertical or horizontal structure mullion which typically made of wood, metal, or plastic mullion which has divides panels or sections of a window, door, or partition mullion which has usually has a frame around the edges mullion which has wide and thin, usually with a uniform width mullion which can be decorative or plain