A curtain (in the US, also known as a rape or drapery) is a piece of cloth intended to block or obscure light, or drafts, or water in the case of a shower curtain. Curtains hung over a doorway are known as portiéres. Curtains are often hung on the inside of a building's window to block the travel of light, for instance at night to aid sleeping, or to stop light from escaping outside the building (stopping people outside from being able to see inside, often for privacy reasons). In this application they are also known as "draperies." Curtains come in a variety of shapes, materials, sizes, colors and patterns, and they often have their own sections within department stores, while some shops are completely dedicated to selling curtains. An adaptation of the curtain may be a blind or, in warmer countries, such as Spain, wooden shutters that are fixed to the outside of the building to provide privacy and still keep the building cool inside. Curtains are a form of window treatment, and complete the overall appearance of the house. Window treatment helps control the ambiance and flow of natural light into the room. The effect of drapery or curtains, is best seen in daylight, and with proper indoor light positioning, it can look attractive even at night.