Question: We have a large fireplace that is missing the damper. As a source of additional heat to the pellet stove, we are considering installing a propane log unit. How do we seal the fireplace so that we can install the propane unit? Answer: If it is a vent-free log, you can install a sheet metal "pan" that fits tightly into the are below the damper. Make the pan 2" wider and deeper than the opening (at a level plan about 2" above the fireplace opening) and bend a 1" edge down. You can then use a lag or masonry nail to fasten the plate to the fireplace, although if you cut it right, it will stay up there just by friction.