PURPOSE: To mount a grill by a suitable holding force in a good external appearance in close contact with a ceiling surface by vertically adjustably providing a latch of a body side to a body.

CONSTITUTION: A holding spring 5 having a flared forked leg acting as a spring force is mounted in an opening resisting direction on a grill 3 mounted in the opening of a body 2, and a latch 4 for latching the leg of the spring 5 is so mounted at the body 2 side as to be vertically adjustably at its position to the body 2. Thus, if the body 2 is deviated from a ceiling surface S, the latch 4 is moved to the body 2 by a screw 8 to eliminate the movement of the positional relationship between the spring 5 for holding the grill 3 and the latch 4, and the grill 3 can be mounted by a suitable holding force in a good external appearance in close contact with the surface S.