One duct section is S-and-drive and the next is TDC/Ductmate/flanged

Stop and ask for the approved adapter or correct fitting. Do not casually mix connector systems or field-cut one system into another.

Verify the required connector type before adapting anything. S-and-drive versus flanged duct is a drawing/spec/shop-standard call, not a habit call.

Rectangular Duct & Fittings 2nd Year YELLOW

Stop if

Always ask when two duct sections have different joint systems.

Watch out

Do not mix connector systems in the field without approval.

Check

Check the piece mark
Check the approved connection detail
Verify both duct ends are meant to connect

Steps

Identify both connection types.
Check piece tags and shop drawing.
Confirm whether an adapter, transition, or different piece is missing.
Photograph both duct ends.
Ask before cutting, drilling, or forcing the joint.

Say this to your foreman

In Rectangular Duct Assembly: S-and-Drive, I'm looking at: One duct section is S-and-drive and the next is TDC/Ductmate/flanged. What should I verify before I cut, drill, seal, cover, move, or install?