How do I build an end-cap out of flat metal in the field

Plain-English answer

1. Measure the exact outer width and height of the raw duct opening. 2. Cut a piece of flat stock sheet metal that is 2 inches larger than those dimensions on all four sides. 3. Notch out the four corners at a clean 45^\circ angle. 4. Use your bar folder or hand seamers to bend a 1-inch flange back at a 90^\circ angle along all four edges. 5. Slide this formed cap box cleanly over the raw end of the duct, secure it with tek screws every 3 inches, and mastic the internal or external seams.

Field checklist

• Measure the exact outer width and height of the raw duct opening.
• Cut a piece of flat stock sheet metal that is 2 inches larger than those dimensions on all four sides.
• Notch out the four corners at a clean 45^\circ angle.
• Use your bar folder or hand seamers to bend a 1-inch flange back at a 90^\circ angle along all four edges.
• Slide this formed cap box cleanly over the raw end of the duct, secure it with tek screws every 3 inches, and mastic the internal or external seams.

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