An awning or overhang is a secondary covering attached to the exterior wall of a building. It is typically composed of canvas woven of acrylic, cotton or polyester yarn, or vinyl laminated to polyester fabric that is stretched tightly over a light structure of aluminium, iron or steel, possibly wood or transparent material (used to cover solar thermal panels in the summer, but that must allow as much light as possible in the winter). The configuration of this structure is something of a truss, space frame or planar frame. Awnings are also often constructed of aluminium understucture with aluminium sheeting. These aluminium awnings are often used when a fabric awning is not a practical application where snow load as well as wind loads may be a factor. The location of an awning on a building may be above a window, a door, or above the area along a sidewalk. With the addition of columns an awning becomes a canopy, which is able to extend further from a building, as in the case of an entrance to a hotel. Restaurants often use awnings broad enough to cover substantial outdoor area for outdoor dining, parties, or reception. In commercial buildings, an awning is often painted with information as to the name, business, and address, thus acting as a sign or billboard as well as providing shade, breaking strong winds, and protecting from rain or snow. In areas with wintry weather, most awnings do not have to be taken down at the end of the summer – they can remain retracted against the building all winter long, or be designed and built for those conditions.