Abstract: This invention is related to a manufacturing process of covering foils of packing boxes extending over at least one edge of the box. The process comprises the steps of cutting slots in a film (3) of rigid transparent material, of glueing a film (4) of flexible transparent plastic material to the prepared film, and of cutting covering foils from the resulting composite material. This invention is also related to the foils made in this way and to the packing boxes provided with such covering foils for the windows.