100mm drywall screws are longer screws designed for fastening thicker drywall panels or for securing drywall to thicker materials such as wood framing or metal studs. These screws typically have a coarse thread and a bugle head design to prevent tearing of the drywall paper and provide a flush finish. They are commonly used in commercial and industrial construction projects where thicker materials are involved. The longer length of 100mm allows for deeper penetration into the framing or studs, ensuring a secure attachment of the drywall panels.