Covering plate formed as a self-supporting cassette construction comprises a frame (4) with peripheral sheet metal sides, a supporting framework (7) made from reinforcing sheet metal parts (8) connected to the sheet metal sides and an upper sheet metal part (9) connected to both the sheet metal sides and the reinforcing sheet metal parts. Preferred Features: The supporting framework has a lower sheet metal part connected to both the sheet metal sides and the reinforcing sheet metal parts. The sheet metal parts are made from steel and are welded together.
