| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw anchor, capable of being screwed with a general- purpose tool on hand without using expensive special tool by using a low-cost disposable holder as a screwing tool, and not penetrating through even a thin board. SOLUTION: A shaft part 22 has a tapered upper half part 22a whose diameter is enlarged toward a head part 23 formed at its end part, while a lower half part 22b is formed with a screw thread 25 on its outer circumference. The screw thread 25 whose diameter is enlarged toward the head part 23 has an equal root width overall. The screw thread 25 has a flat part 24 at its top part, which inclines toward the head part 23, and whose width is narrowed toward the head part 23. A bolt-screwing hole 26 is penetratingly formed in the shaft part 22 along its axis, while plural bolt-screwing projecting stripes are formed along an axial direction on an inner circumferential face of the bolt-screwing hole 26. Engaging parts 29 for a screwing holder 31 are recessed at plural positions on a periphery of the bolt-screwing hole 26 at an end face of the head part 23.
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