Which statement about SEMs screws is true?

SEMs screws, or Self-Embedding Metal Screws, are known for their specific design that typically includes a locking washer. This locking feature enhances the screw's ability to maintain a secure grip, which is especially important in applications where vibrations or movement may loosen fasteners. By incorporating a locking washer, SEMs screws help to prevent the threaded fasteners from loosening over time, ensuring reliability and stability in various assemblies.

The other options do not accurately reflect the characteristics or common uses of SEMs screws. While SEMs screws may be used in some scenarios involving electrical components, their primary function is not focused on electrical connections. Additionally, while they are designed for metal applications, they are usually not made of plastic; instead, they are constructed from metals that provide the necessary strength and durability. Furthermore, not all SEMs screws are self-tapping; their design can vary based on the application, and they may require pre-drilled holes for optimal installation.