The Fn key, short form for function, is a modifier key on many keyboards, especially external keyboards, and is not available for mobile devices. For use in a compact layout, combine keys which are normally kept separate. It-Alt + FN is typically found on laptops due to their keyboard size restrictions. It is also found on many full-sized "multimedia" keyboards as the F-Lock key. It is mainly for the purpose of changing display or audio settings quickly, such as brightness, contrast, or volume, and is held down in conjunction with the Caps Lock to change the settings.