Abstract: In each arm of a profiled part a notch is made. The notch has two convergent edges forming an angle substantially equal to the angle to be made with the profiled parts. The notch is designed of such a size that the bending can be easily made by applying a compression stress combined with a folding stress in order to reduce at a minimum the extension of lengthening during the folding without reaching the breaking limit of the material constituting the profiled part.