The tympan flanges connect the tympan to the hinge assembly (heel iron). The tympan needs to be removed from the press for covering. The flanges are made from a piece of 3/4 inch steel. There are nuts let in to the tympan which catch the screws. The tympan is lined with a layer of 1/8 x 3/4 inch steel to keep it from warping when covered.