Panel of decorative fabric hung to regulate the admission of light at a window and to prevent drafts. Curtains made of a heavy material, arranged to fall in ornamental folds to the floor, are called draperies. Mosaics from the 2nd–6th century show curtains suspended from rods spanning arches. From the Middle Ages to the 19th century, curtains ranged in style from simple to ornamented; beds were often curtained on all sides. In the 20th century, synthetic fabrics and mechanical devices for opening and closing curtains simplified their installation and use.