A method of permanently bending a first part of a subject body having non-linear elastic properties about a bending line to a desired angle relative to a second part of the body in which a first set of data is produced from similar bodies of the amount of permanent bending obtained as a function of different amounts of angular displacement of the first part, the first part of a subject body is permanently bent to a first angle different from said desired angle by angularly displacing the subject body's first part by an amount determined by the first set of data and thereafter the first part of the subject body is further angularly displaced from the first angle to permanently bend its first part to the desired angle.