Sash window

A sash window or hung sash window is made of one or more movable panels, or "sashes", that form a frame to hold panes of glass, which are often separated from other panes (or "lights") by glazing bars, also known as muntins in the US (moulded strips of wood). Although any window with this style of glazing is technically a sash, the term is used almost exclusively to refer to windows where the glazed panels are opened by sliding vertically, or horizontally in a style known as a "Yorkshire light", sliding sash, or sash and case (so called because the weights are concealed in a box case). The oldest surviving examples of sash windows were installed in England in the 1670s, for example at Ham House. The invention of the sash window is sometimes credited, without conclusive evidence, to Robert Hooke. Others see the sash window as a Dutch invention.