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Apprentice Q&A · #091

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

2nd YearField ModsYELLOW · Check First

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.

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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

Ask Foreman

Hey boss, I’m checking field mods: How do I build an end-cap out of flat metal in the field? I found the likely issue and want to verify the next step before I lock it in. Do you want me to adjust it now or check the drawing/detail first?

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Verify before acting

Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

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