Stop screws from loosening due to light vibration. These screws have a washer with uneven ends that bite into the screw head and the mating surface as you tighten them. While they're not as vibration resistant as tooth lock washers, they're a good choice for electrical panels, light fixtures, and other light duty assemblies. Also known as Sems screws, the washer rotates freely but is permanently attached. Pan heads have a moderate height and width profile, offering a middle ground between narrower button heads and wider truss heads. The Phillips drive easily aligns with drivers and withstands more torque than slotted drives, but drivers slip when you apply too much force.

Length is measured from under the head.