We have a masonry fireplace with an arched opening. The lintel is a square behind the arch, in other words, the bricks form an arch in front of the lintel (hope that explains it clearly). We’re trying to figure out if we can buy and install an insert with glass doors or if it has to be a screen. We really don’t want to pay two grand for a custom door given the fact that we just made major repairs on the chimney.