The top part of one inner bolt which matches the blank hole channel of the outer hollow screw is also conical. The rear is provided with a thread and a tetragonal body for holding.
一与外空心螺钉的盲孔道相匹配的内螺栓，内螺栓的尖端部位亦为锥形，尾部设有螺纹和供握持用的四方体。
3
Connecting bolts are arranged in the plugging conical points, and an anti-rotation key and an outer six-square sleeve which can realize the linkage are arranged on the screw bolt.