Fixed window: A window that cannot be opened, whose function is limited to allowing light to enter. Also known as picture window.
Fixed panel. An inoperable panel of a sliding glass door, single hung window or slider window.
Frame: The enclosure in which window sash or door panels are mounted.
Flashing: Strips of sheet metal bent to fit the angle and divert water away from a skylight or window.
Fogging: A deposit or film left on the inside surface of a sealed insulating glass unit due to extremes conditions, temperatures or failed seals.
Fusion-welded: Strong, weathertight method of heat-joiningmaterials by melting them together with extreme heat resulting in the materials uniting into a one-piece unit.