American Chop Suey was the original plan. But the grocery store was out of elbow macaroni, so I looked for something close to substitute, and chose these little mini-wheel pastas. They looked like they might have some model railroad potential as gears or big HVAC fan units. Two mini-wheels were spray painted silver. An 8-nub Lego block was turned upside-down, with a piece of styrene to cover the open Lego bottom (now the top). The Lego block was spray painted HVAC green. The mini-wheels were glued on top. Placed on top of a building, the Lego nubs space the HVAC unit up off the roof a bit. Another bit of styrene on the side suggests an electrical disconnect box.