Countersink
Affiliate link — we may earn a commissionA countersink is a conical recess cut into the surface of a board so a flat-head screw sits flush with or below the surface. A countersink bit has a tapered cutter that widens the top of a pilot hole into a cone that matches the screw head's angle (usually 82 degrees for wood screws). Combination bits drill the pilot hole and countersink in one pass. Countersinking is required for any flat-head screw in visible work. Without it, the screw head sits proud of the surface and catches on anything that slides across it. You can also counterbore deeper and plug the hole with a wood dowel for a hidden fastener.
Why It Matters
On furniture, cabinets, and trim, a screw head sticking up above the surface looks sloppy and catches on hands, clothes, and anything placed on the surface. Countersinking takes 3 seconds per screw and makes the difference between amateur and clean work.