A short Ductmate rail usually means the rail needs to be replaced or the duct section needs to be remade. Before escalating, check how short it is, whether the corners can still seat, and whether the flange holes still line up cleanly.
Ask when connector type, gasket, cleat/bolt schedule, pressure class, or manufacturer detail is unclear.
Watch out
Do not cut, slot, stretch, or force rail/hole alignment without approval.
Check
Measure how short the rail is and write the amount down before you move the piece.
Check whether the corner clips can still seat fully at both ends of the short rail.
Check whether the bolt holes still align across both flanges without forcing them.
Do not try to stretch, slot, or force the rail into position.
Set the section aside, mark the issue, and bring the measurement with you if it needs approval.
Steps
Measure how short the rail is and write the amount down before you move the piece.
Check whether the corner clips can still seat fully at both ends of the short rail.
Check whether the bolt holes still align across both flanges without forcing them.
Do not try to stretch, slot, or force the rail into position.
Set the section aside, mark the issue, and bring the measurement with you if it needs approval.
Say this to your foreman
I cut this Ductmate rail short by about inches. The corner clips [can / cannot] seat fully and the bolt holes [do / do not] align. Do you want this rail replaced, the section remade, or is there an approved recovery?