How far out from the side of the duct are holes for anchors usually made?

• A. 1/4 inch
• B. 3/4 inch
• C. 1/2 inch
• D. 1 inch

Answer: (C)

Anchor holes should be placed at a safe distance from the duct edge to hold the hanger securely without weakening the duct wall. About one-half inch from the side is the standard practice. This distance leaves enough metal around the hole to resist tearing when the fastener is tightened, and it keeps the hole away from bends and seams where distortion could occur. If the hole is too close to the edge, the edge can crack or tear under load; placing it farther away offers little extra benefit and can interfere with proper hanger alignment.