Abstract: A decorative trimming system includes at least one substantially straight length of decorative crown molding installed along a ceiling and wall junction and at least one stabilizing member secured between the rear surface of the crown molding and the ceiling and wall junction. The stabilizing member includes a predetermined length and a predetermined shape in a direction transverse to the predetermined length. The predetermined shape is defined by a pair of side edge surfaces extending the length of the stabilizing member and a substantially smooth uninterrupted front surface extending the length of the stabilizing member, abutting rear surface of the crown molding and preferably adjoining each of the pair of side edge surfaces. Arrows and text indicia may be also provided for communicating orientation of the stabilizing member during securement to the ceiling and wall junction as well as during mitering ends of the decorative molding on a miter saw.