1. The flexible air duct is taken out of a hole where is opened sufficiently on the upper side of the box. The required length is measured and marked with a felt marker. The duct is cut by a knife and then the wire as well. The rest will be pushed into the box again for the following use.

2. The inner duct is exposed by pushing the outer jacket and the insulation layer. For uninsulated ducts, there is not such a process. The inner duct is pushed over the connection piece minimum 25 mm. The connection piece is sealed with aluminium tape at least two windings around the duct. Then the clamp is attached tightly.