Abstract: It comprises a plurality of flat strips (1) and a plurality of dividing walls (2) arranged transversally to the flat strips (1), the length of each flat strip (1) being substantially equal to one of the dimensions of the box (4), and each dividing wall (2) being set between two adjacent flat strips (1) or between one flat strip (1) and a wall of the box (4), and at least some of the dividing walls (2) having a flap (3, 3a) at each end, and each of the flaps (3, 3a) being glued to a flat strip (1) or to the wall of the box (4). The divider can be manufactured in a totally automated continuous process, and allows a remarkable saving of materials while its strength is not reduced.