Some videos that show how to snap together a section of round metal duct also show that it can be taken apart just by dropping it on the floor. (e.g.https://www.youtube.com/watch?v=seGVzTHFFgU ) After a piece of round duct is assembled, do people ever use screws to keep it together? Is sealant applied along the seam sufficient to do that? Do miscellaneous things like duct hangers and joints with other pieces of duct keep the seam from un-snapping?