There is a gap at the S-lock corner

Correct the fit-up first. A corner gap usually means the S/slip is not seated, the duct is out of square, or the drive/corner is misaligned.

Fix the seated side before finishing the drive. If the S-lock is not fully seated, the drive side may never pull the corner tight.

Rectangular Duct & Fittings 2nd Year YELLOW

Stop if

Ask when the gap remains after reseating or if the corner is damaged/crushed.

Watch out

Do not seal or cover a joint that is only partly seated.

Check

Re-seat the S side
Check the corner gap
Verify the duct is not twisted or carrying weight

Steps

Inspect the corner before sealing.
Check S/slip seating and drive seating.
Check whether the duct is square.
Re-seat or rework the connector if possible.
Seal only after the corner is mechanically correct.

Say this to your foreman

In Rectangular Duct Assembly: S-and-Drive, I'm looking at: There is a gap at the S-lock corner. What should I verify before I cut, drill, seal, cover, move, or install?