S and drives are used in sheet-metal ductwork to:

• A. are driven only with wooden mallet.
• B. are used for sheet-metal siding.
• C. connect transverse joints of ductwork.
• D. prevent air leakage.

Answer: (C)

S and drives are a fastener system used to secure the joints where duct sections meet across the duct’s cross-section. When sheet metal ductwork is assembled, sections are joined end-to-end, forming transverse joints that run across the duct. Using these fasteners locks the joints in place, keeping the duct aligned and structurally sound as air flows through it. While proper sealing handles leaks, the primary purpose of S and drives is to connect those transverse joints.