Couplings slip inside the ends of two round ducts to become joined with each other then sheet steel screws are mounted to hold it in position. Couplings may very well be essential at a certain sizing for example connections 18” and bigger. The shaded place within the image underneath could https://finnpeuhu.rimmablog.com/35708831/how-oval-conduit-can-save-you-time-stress-and-money