| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw such as a tapping screw, a small screw, etc., allowing even an unskilled person to easily and vertically screw in a screwing material. SOLUTION: Only a head end part of a male screw 4 is made into a three-line screw, and the other part is made into one-line or a two-line screw. A screw 1 makes contact with a lower hole or a screw hole opening peripheral edge part at three points by three screw threads of a three-line screw part 4b at the time of screwing the screw 1 into the lower hole or the screw hole provided on the screwing material, and a flat surface including these three points decides a screwing direction (driving direction) of the screw. Consequently, it is possible even for an unskilled person to easily and vertically screw the screw 1 into the screwing material. It is possible to provide a projection on the head end part of the male screw 4 so as to perform the same function as the three-line screw part 4b.
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