Sharp internal teeth dig into surfaces to resist heavy vibration while the smooth outside edge provides a finished look.

The flat washer distributes holding pressure and protects delicate surfaces from damage while the split lock washer adds tension to prevent loosening from small amounts of vibration.

The flange distributes pressure across a wider surface, eliminating the need for a separate washer.

With a deeper drive than flat and rounded head screws, socket head screws withstand more torque for a tighter hold. Install in a counterbored hole or above the surface.