Abstract: A metal core is obtained from a continuous metallic strip, having proper characteristics as far as plasticity and ductility are concerned. This metal band or strip is die-cut to provide a reticulate structure formed by hexagons rather contracted lengthwise. These hexagons constitute a lineup in such longitudinal direction and, in a later phase, are subjected to a folding operation so that their larger sides similar to adjacent hexagons form the central portion of the channeled section, while the joints remain on the side portions of the channeled section. Besides, the side apices of these hexagons extend, forming small flaps which, in turn, make the joints in between take the center line of the mentioned side portions of the channeled sections.