We put the new furnace (replacing the old one) closer to the wall with the flue pipe, displacing an ancient slop sink (which vanished from the end of the driveway in about an hour) in the process. I “plugged” the drain with a twist of paper towel until the installation was done:
The overexposed blue-hot glow comes from the LED worklight on the right.
Despite being chrome-plated brass, the nut at the base of that vertical chrome pipe was firmly corroded to the short nipple emerging from the iron tee. After a few minutes of fruitless wrenching, I deployed a Dremel cutting wheel, slit the nut, gave it a shot with a chisel, and it popped loose. A rubber cap clamped around the nipple finished the job: