Plate glass is a type of flat glass that was once commonly used in glass doors, mirrors, and windows.
So, how is plate glass made? The first way of creating truly flat glass was done by pouring molten glass onto metal tables or plates and rolling it flat before leaving it to cool. This method made the plates of glass for which plate glass is named and was the traditional way of manufacturing windows and mirrors. Plate glass could be made in various weights or thicknesses. Today, flat glass is primarily made through the float process, which requires less space. While many consumers still use the phrase plate glass, especially to refer to large windows (e.g. in storefronts) or doors, the float process – which makes float glass – all but replaced the plate glass manufacturing process by the 1950s.