Abstract: A folding unit for a cardboard packer is disclosed, which is adapted to close and seal a lid of a cardboard box. The folding unit comprises a conveyor for transporting the cardboard box to the folding unit, a transport device for moving the box and/or a folding device into contact with each other, and further also a catch that is arranged adjacent the conveyor for stopping the box at a folding position, wherein the folding unit further comprises a sensor for detecting when the catch has stopped a box, for activating the transport device such that the box can be final folded.