I have a fireplace that in the burn area is metal on the sides of the box and top then tapers up in the back to a metal damper door that opens and closes with a lever, up from the damper door it angles back again then goes straight up into the ceramic square chimney and straight up. The chimney is surrounded by brick and the whole firebox is surrounded by real rock and is all in a corner. I realize this may be hard to visualize by me saying what it is but am wondering how to install an insert in this or if an insert is even safe to put in this set up. We have burned wood in this fireplace for 5 years now and am tired of throwing away all the heat. Any help and suggestions would be of great help. I have considered the wood burning insert from Northern Tool catalog. Does anyone have any experience with this insert?