Question: Hope you can help. I am an Architect with a client problem new to me. Here it is...... He has a zero clearance wood burning fireplace, whose manufacturer is unknown, which he recently had a mason remove the "1/2" thick ceramic liner and install new 4" thick firebricks. The question is, is it safe to use the fireplace as in the past? Some of the metal box is exposed at the very top of the unit just as it was in the past. Answer: Chances are that it is safe to use. This assumes no intake air vents that have been covered. The sheet metal showing up top is normal in pre-fabs. Next time you run into this, be aware that generic replacement panels can be purchased and cut to size. These are usually provided by local chimney sweeps.