The head of socket screws has a hexagonal socket or internal drive. In most applications, the inserted screw must sit flush with or just below the surface of the workpiece, hex socket countersunk screws—also known as flat or flat head socket screws.
The tool needed to tighten and loosen a screw will reveal whether it is a socket screw. The basic rule of thumb is straightforward. A socket screw requires a specific internal wrenching drive, an Allen or hex key. The sloping shoulder design of countersunk socket screws is typically at an angle of around 82 degrees, enabling the screw to embed itself in the surface through a previously drilled countersunk hole.
