Which method is not suitable for joining lengths of round duct?

Joining lengths of round duct requires methods that ensure a secure and airtight connection. Drive clips are often used for joining rectangular ductwork but may not be suitable for round ducts because they do not provide the necessary grip and seal needed for circular connections. On the other hand, screws, rivets, and even zip ties can effectively secure round duct sections.

Screws and rivets can penetrate the duct material and create a strong mechanical bond, offering durability. Zip ties can be employed for lighter applications or when a temporary solution is required, as they provide some level of flexibility in securing ducts without causing damage. Therefore, drive clips are not appropriate for round ducts, as they do not adequately address the needs for secure and proper sealing in this context.