PURPOSE: To perform assembling and adjusting operation excellently by providing a rail to the center lower part of a window frame at right angles to the window frame, and fitting a door opening/closing rod rotatably between a slider which slides on the rail and controls the direction of a cuckoo body and an opening/closing door.

CONSTITUTION: One end of the rail 2 is fixed to the center lower part of the window frame 10. The rail 2 is provided to the window frame in the internal direction of an external box at right angles. Then, the slider 4 which is guided by the rail to slide is provided on the rail 2. A projection part 32 which controls the cuckoo body in engagement with the tail part of the cuckoo body is implanted in the slider 4. The cuckoo body 24 rotates under control while its tail part 24a engages with the projection part 32 and is prevented from contacting the door 18. Consequently, the cuckoo body is assembled while unitized as a cuckoo body jumping-out mechanism, so the assembling and adjusting operation is performed excellently.