Frame filler is a term used to describe the material used to fill in the space between the frame and the glass of a window. The three crossword solutions for this term are PANE (4 letters), ART (3 letters), and ZAQF (4 letters). PANE refers to a sheet of glass, usually framed, that is used to form a window or door. ART is an abbreviation for ART glass, which is a type of decorative glass used to fill the space between the frame and the glass of a window. ZAQF is an acronym for zinc alloy quatrefoil, which is a type of metal used to create a decorative pattern in the frame filler.