A frame defining a central region for supporting a thin mirror film across the central region within a film plane. The frame includes four supporting members each joined together and having a longitudinal axis, an adhering surface and a forward surface. A supporting ridge is provided on the forward surface of each frame member being generally parallel to the longitudinal axis thereof. The supporting ridge is positioned intermediate the adhering surface and the central region. The supporting surface protrudes from the forward surface by a predetermined distance and is adapted to support a thin mirror film tautly across the central region within the film plane.
