Units suitable to realize the notching of the corners on metal sheets. The depth of the slot can be increased by varying the position of the unit, up to a maximum of 150 x 150 mm. The rounding off angle is 90 °, or, by using the variable angle tool, can be changed from 30 ° to 180 °. As well as the punching units, the notching units are to be placed under the press, and the return of the punch is independent from the ram of the press.