| 摘要 |
In a fastening portion for fastening an upper retaining portion and a lower retaining portion by means of a mounting screw, the upper retaining portion has a screw hole and a cylindrical guide formed around and above the screw hole. Further, a projection is formed on the inner wall of the cylindrical guide at an upper portion thereof. In a loosened condition of the mounting screw where it is disengaged from a screw hole, the head portion of the mounting screw is caught to be retained by the projection. The upper portion of the cylindrical guide is tapered so that it has an inner diameter smaller than the diameter of the head portion of the mounting screw. Accordingly, even when the upper retaining portion is turned upside down in the loosened condition of the mounting screw, the mounting screw does not fall down from the upper retaining portion.
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