Flat Oval Spiral Duct Observe the under video clip to begin to see the set up of oval duct and fittings. Notice the reducer getting used is undersized on its collar allowing the oval duct to slide over the collar. They can be using Unistrut with threaded rods as hangers https://lanefwlan.gynoblog.com/35700234/the-definitive-guide-to-oval-conduit