Countersink
A cone-shaped recess drilled into wood that allows a flathead screw to sit flush with or below the surface, enabling concealment with wood plugs or filler.
In-Depth Explanation
Countersinking is a fundamental technique in wood joinery and finish carpentry that creates a clean professional appearance by eliminating protruding fastener heads. A countersink bit creates a conical recess matching the angled underside of a flathead screw, while a counterbore creates a flat-bottomed hole for recessing deeper and covering with a plug. Combination drill-countersink bits that create the pilot hole and countersink in one operation are among the most popular workshop accessories. In hardwood and near board edges, pre-drilling and countersinking are essential to prevent splitting. Matching wood plugs cut with a plug cutter create nearly invisible fastener concealment.
Usage Example
I used a combination drill-countersink bit to pre-drill each screw hole in the oak, then covered the heads with walnut plugs for contrast.