Shaping and joining technique: it refers to the rectangular bending of the edges of round or oval metal sheets with a bending machine. As far as we know, the history of bending began at the beginning of the 20th century with the bending of the first tin cans. Bending is used to join metal sheets, different thin plates or tubes – by welding, folding, riveting, adhesive bonding or soldering. In many cases, the bending is only used to reinforce the material.