Stainless steel screen holder and the screen. Fitted on top of the heater.

It can be replaced easily by opening the back end big screw with a Torx T20 screwdriver and removing the bottom panel. Then there is another hole inside after removing the bottom panel, under the long screw hole is another hole. Place a screwdriver Torx T20 and push it deep until it reaches the inside of the top panel, and unscrew the screw there until you are sure it is loose, probably some 15 full rotations needed. Now you can remove the top panel, and replace the screen and/or the broken glass lining. When putting back, it is important to tighten again first the internal screw, and then the long screw very tight.