Self-tapping screws tap their own threads into a pre-drilled pilot hole, whereas self-drilling screws feature a drill-bit point that can drill their own hole and tap threads in a single operation without pre-drilling.

Yes, for standard self-tapping screws, drilling a pilot hole is highly recommended. The size of the pilot hole should match the inner thread diameter of the screw to ensure optimal grip and prevent material splitting.

Galvanized self-tapping screws are coated with a protective layer of zinc, which provides outstanding corrosion resistance and durability, making them ideal for outdoor and high-humidity applications.

The rubber washer (often EPDM) creates a tight, waterproof seal when compressed. This prevents rainwater and moisture from leaking through the screw hole into the roofing structure.

While they can physically be reused, it is not recommended for critical applications. Re-using them in the same hole can lead to loose fits and stripped threads, significantly reducing their holding power.

Pan head self-tapping screws are highly versatile and commonly used to secure thin metal sheets, wood, plastics, and fiberglass composite materials.