In my opinion, the ‘80s saw the most significant development in HVAC duct fabrication of any during the past half-century. So much so, that I have to split the 1980s into two stories: One is in the March issue of SNIPS hereto, and another is due to be published in the April issue. I covered the ‘70s in a previous issue.
As the late ‘70s closed out there were many different types of connections. Some were regional, others were constructed to contractor preferences regarding time to shop fabricate and for field hanging: