Abstract: The retainer clip is adapted to be positioned between an inwardly extending flange at the back of a picture frame and backing material located within the frame behind a picture in the frame. The retainer clip includes a resilient body, structure on the body for engaging the inwardly extending flange at the rear edge of the picture frame and structure on the body for engaging the backing material. The structure for engaging the backing material includes at least one prong, detent or barb positioned to engage the backing material.