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Hexagon head screws and large hexagon bolts are, as their name implies, external threaded fasteners with hexagonal heads, designed to be turned using a wrench. Hexagon screw outside the screw head is round, the middle is concave hexagon, and hexagon screw is usually seen more screws into the hexagon edge. Hex screwdriver looks like '7', with two sections of hexagonal steel bar cut in bending 90 degrees into a hex screw wrench, hardware stores have to sell.
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