To use a bolt and a nut of the desired size sufficient for securing the required tension within the limited space by separating the nut into a cap nut part to threadedly engaged with the bolt and a tool engagement part.

In a connector comprising a bolt 50 and a nut 40 to join ceiling beams 23A, 23A, the nut 40 is provided with cap nut parts 41, 41 to be threadedly engaged with the bolt 50, and tool engagement parts 42, 42 connected thereto which are smaller than the cap nut parts in the outside diameter. The outside diameter of the cap nut part 41 is the minimum size required for threadedly engaged with male screw parts 51A, 51B of the bolt, and the outside diameter of the tool engagement part 42 is the minimum size required for engagement with a tasting tool. The bolt 50 and the nut 40 of the desired size sufficient for securing the required tension can be used within the limited space around a bolt fastening part.