US Fasteners, 1/2", 18-8, Phillips flat head

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  Wood screws

  Screws with a smooth shank and tapered point for use in wood.

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  Sheet metal screws

  Screws with large threads for use in sheet metal sometimes also used in plastic, fiberglass or wood.

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  Machine screws

  Screws with machine threads for use with a nut or in a tapped hole.