position as illustrated by the solid line in fig6 the lever 28 and the pawl plate 24 are turned to their latch releasing positions thus releasing the latch plate 22 with this the striker 10 of the auxiliary door part 7 is released from the second lock device 11 so that the auxiliary door part 7 can be opened upon this the engaging portion 24a of the pawl plate 24 rides on the arcuate edge 22b of the latch plate 22 so that the pawl plate 24 and the pivotal lever 28 are kept in their latch releasing positions thus thereafter the key plate 18 of the key cylinder 13 is prevented from turning from its neutral position to its first lock releasing position accordingly when the auxiliary door part 7 is kept opened releasement of the first lock device 9 by manipulating the control device 12 is impossible this is quite advantageous when considering the danger which would arise when the main door part 4 becomes opened with the auxiliary door part 7 opened when the auxiliary door part 7 is closed the striker 10 of the part 7 is brought into engagement with the latch plate 22 and pushes the same with this the latch plate 22 is turned to its latched position permitting the engaging portion 24a of the pawl plate to come into locking engagement with the angled portion 22c thereof with this the pawl plate 24 and the lever 28 are both turned to their latch positions by the forces of the springs 26 and 30 thereafter the key plate 18 of the control.