existing boiler flame shield has a little window to view flame - but you can NOT see the flame, not possible at all (no Effin way!) , so I modified it to be totally removable without tools. Thumbscrew screws into a Tee-nut installed from the underside. I cut away the tab for the anchor screw and relocated it to use with the Tee nut (1/4"-20 tpi). A Dremel was most helpful, as was a pop rivet tool.