The microwave over my stove expired. I pulled it down, and discovered that the ductwork to attach the fan to the outside world was misplaced: it's about two inches to the right of where it should be. The builders applied tape and sheet metal screws to attach the flap and duct to the old microwave out of line with the fans.
I'd rather not produce a repeat of that charming bit of 'craftsmanship'd. Can someone help me plan a proper repair? There's a round duct that goes out through the wall of the house, and it's bonded to the rectangular duct that you can see in the picture. I've pulled all the sheet-metal screws and tape to get a look at what's going on. Hypothetically, I'd want to somehow detach this 'box' from the 'pipe', and mount a new one with a suitably asymmetric hole for the pipe to compensate for the failure of the center of the pipe to match the center of the stove. I don't know how the two pieces of ductwork were connected to start with, and I'm loath to attack what I've pictured here with a sawzall (or equivalent) without a clear plan of what I'll do thereafter.