The SKK molding is fitted with injected glue. It can be applied on duct walls up to 2 mm thick (Gauge ≈14)
The thicker side of the SKK must be inside the duct. Apply the SKK molding so that the duct wall enters as deeply as possible into its pocket.
Both ends should meet at a straight section of the opening. Cut the SKK at the right length so that both ends press slightly against one another without overlapping.
Turn the knobs till they hit the stops and insert the inner door panel inside the opening at an angle. Then straighten the door, pull it lightly to center it and tighten the knobs.