Divided backrest for an automotive vehicle and process to hinder the relative motion of the two segments of the divided backrest

The rest has a supporting device for a rod of a middle head rest and designed in one of segments (2, 3) close to a joint, where the segments are turned around a horizontal axis. The supporting device is connected with a locking mechanism, which consists of a releasing position, in which the segments of the back rest change their position together and a locking position, in which the segments of the back rest are in fixed position. An independent claim is also included for a process to hinder the relative motion of two segments of the divided backrest.