In order to lock the door proceeding from the open position, a locking bar is brought into the locked position under tension of a spring element, in which locked position a closing force acting on the locking bar is determined by the spring element, and, in order to unlock the door, the locking bar is brought out of the locked position into an unlocked position with the aid of an actuating force that is not applied by the spring element, and, after the striker has moved out of the locked position, the locking bar moves into the open position by the force of the spring element.