| 摘要 |
A screw has a head portion and a threaded portion. The head portion has an undercut slot extending across it. The slot has a flat floor and sloping sides and the width of the floor of the slot is greater than the width at the top opening of the slot. A matching bit has a shank portion and a flat portion. The flat portion of the bit is not as wide as the top opening of the slot. The flat portion has a foot extending from each end. Each foot has a flat base and inwardly-sloping sides
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