A flat sheet is convoluted using a press-brake die to form the individual convolutions. This method is used primarily in the manufacture of bellows for rectangular Expansion Joints described in Section 5. Many convolution profiles can be achieved using this method. The most common styles are the "U'' profile and "V" profiles shown in Figure 5.9. Material availability and press-break tooling limit the length of the rail. Longer lengths can be manufactured by splicing the rails together with longitudinal welds.