Abstract: A window frame construction particularly useful in a manufactured housing unit to provide a structure for receiving and supporting at least one window and to provide coverage of ends of siding applied to the exterior of the housing unit. The window frame includes a window body member to generally circumscribe an opening in the housing unit, with a J-rail return member integrally formed therewith to provide a flange member for attachment of the window frame to the housing unit and to cover and secure ends of the siding in a slot formed between the flange member and the return member of the J-rail return. The return member has sufficient width to cover the siding ends even when the siding contracts during lowered temperatures. The window frame, in the preferred form, is constructed from extruded vinyl, and it is used principally for vinyl siding.