Abstract: An apparatus, method and system for a window assembly for insertion into an opening in a window supporting structure including, but not limited to, a building wall or door, or a mobile or automotive vehicle. Frame pieces are adapted to fit into opposite sides of the opening and be releaseably secured into position without the window glazing or any insert in place. This allows the frame pieces to be installed by one person. The frame pieces are translatable relative to one another over a range to accommodate different thickness openings. A glazing or insert can independently installed in a frame piece. Securing structure can be adapted to accommodate different thickness glazing or inserts.