Originally Posted by Varroa
I use EMT conduit hangers. You can bolt them back-to-back with a short 1/4-20 screw, nut, and star washer. They cost less than a buck each. Sizes go from 3/8" to 2" inches. They make great mounts for attaching extra water bottle cages, pumps, and anything else that’s round and 2" or less in diameter. Replacing the supplied screws with thumb screws allows removal without tools.