An S-cleat that is not fully seated means the raw edge of the duct is not fully inside the S. The joint can look connected but still gap and leak under pressure.
Ask when the S-cleat is damaged, too loose, wrong size, or the duct edge will not seat without deforming.
Watch out
Do not seal over an S-cleat that is not fully seated.
Check
Look at the S-cleat from the end and confirm the duct edge is fully inside the S channel.
If it is not seated, check for out-of-square duct, a bent S, a size mismatch, or debris in the connector.
Re-engage by starting at one corner and working across progressively instead of forcing the whole side at once.
If the S is bent open or crushed, replace or correct the S before trying again.
Check all sides after re-seating and make sure there is no daylight at the edge.
Steps
Look at the S-cleat from the end and confirm the duct edge is fully inside the S channel.
If it is not seated, check for out-of-square duct, a bent S, a size mismatch, or debris in the connector.
Re-engage by starting at one corner and working across progressively instead of forcing the whole side at once.
If the S is bent open or crushed, replace or correct the S before trying again.
Check all sides after re-seating and make sure there is no daylight at the edge.
Say this to your foreman
My S-cleat is not seating fully on the [top/bottom/side]. The duct edge is [visible / partially out]. Do you want me to re-square and re-seat this section, or does the S-cleat need to be replaced?