Frame. A window frame is the framework that surrounds and supports the entire window system. It is comprised of the head, jamb and sill. Head. The head is the main horizontal part forming the top of the window frame.Window frames can be made of vinyl, fiberglass, metal, or wood (which may be clad with aluminum or vinyl on the exterior portions). Higher-quality (and generally costlier) windows have better weather stripping to keep air from filtering in around the sashes.