What type of seam would not be used to connect a rectangular take-off onto a rectangular duct?

A Pittsburgh seam is generally used for connecting two pieces of sheet metal, particularly to create a neat, interlocking joint that is effective in rectangular ductwork applications. However, it is not typically employed for connecting a rectangular take-off to a rectangular duct. The Pittsburgh seam is more suitable for joining duct sections where the edges are folded into a specific shape, facilitating a strong bond when two panels are connected.

In contrast, options such as flange out and screw provide a method that allows for the proper alignment and secure fastening of take-offs to ducts. Hammerlock seams offer a strong connection and can accommodate changes in direction, while welding, although less common for HVAC ductwork, can also be effective in situations requiring a sealed, permanent joint. These alternatives are more suited to the task of connecting duct components, as they ensure a reliable airflow and structural integrity.