Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin, although lead and various low melting point alloys were used in the past. This method gives the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass. Float glass is used for smaller windows in domestic housing, whereas larger windows are made from toughened glasses. Glass is used for windows for both aesthetic and functional purposes, allowing the occupants to see out and at the same time allowing light in.