Abstract: A device for covering an opening in a masonry provided on its surface with tiles or plates comprises a holding member (7) for a permanent magnet (8) which cooperates with a ferromagnetic member provided on the inner side of the cover member covering the opening and provided with tiles or plates. The holding member (7) is provided via a predetermined breaking point (12) with a protrusion with a threaded bolt (6) which can be screwed into the threaded bore (5) of a frame surrounding the opening to be covered. After detaching the protrusion along the predetermined breaking point (12), the holding member (7) can be connected with an anchoring member anchorable in the masonry, which anchoring member comprises a plate-shaped section which can be inserted into a slot (15) of the holding member (7) (FIG. 3).