Muntin

A muntin in US usage is a strip of wood or metal separating and holding panes of glass in a window. Muntins are also called "muntin bars", "glazing bars", or "sash bars". Muntins can be found in doors, windows and furniture, typically in western styles of architecture. Muntins divide a single window sash or casement into a grid system of small panes of glass, called "lights" or "lites".