| 摘要 |
PROBLEM TO BE SOLVED: To prevent to release the fastening condition easily, by the third person. SOLUTION: A pair of fastened members 21 get butted each other are fastened by a hexagonal bolt 11 and a hexagonal nut 12 screwed each other, and a special nut 13 is screwed to the shaft part 11a of the hexagonal bolt 11 inserting the hexagonal nut 12. At the inside at the front end side of the shaft 11a of the hexagonal bolt 11, an engaging hole 13b having a regular pentagonal cross section where a special form of tool is engaged is provided. Between the hexagonal nut 12 and the special nut 13, a lock ring 17 abutted by the hexagonal nut 12 and the special nut 13 is fitted to the shaft 11a of the hexagonal bolt 11, being rotated integrally together with the hexagonal bolt 11. The special nut 13 is held in a collar 14 for special nut, and the engaging hole part 13b of the special nut 13 is exposed from the collar 14 for special nut.
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