Abstract: In the manufacture of packing containers from laminated material contact between the inner layer of the material and the contents is avoided by doubling up the cut edges present in the packing container. It has proved to be difficult to perform a secure folding and sealing of the folded edge without damage to the material, since the outer, water-tight layer of the material consists of very thin, heat-sensitive thermoplastic. This difficulty is overcome by carrying out the folding and sealing of the edge of the material web gradually while at the same time supplying heat or glue. By supplying the sealing-promoting agent as late as possible during the course of folding, damage to the material as well as to the folding arrangement is avoided.