Describing a screw or bolt that has been drilled into a surface so its head sits flush with or below the surface rather than sticking out.
From counter- + sunk (past participle of sink). The term combines counter- (meaning a countersinking action) with sunk, emerging in woodworking and metalworking in the 18th century to describe the beveled hole that allows fasteners to sit level.
Countersunk screws are why fancy furniture looks smooth and polished while cheaper stuff has screw heads poking out—it's not just about looks though, flush screws are safer and less likely to snag on clothing!
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