Threads with double spirals grab thin-gauge sheet metal for a secure hold without damaging the material. As these screws tap, the threads engage along the whole length to prevent overtightening and ruining the threads. Also known as Fastite, they have a triangular shank and may have a slightly different diameter than standard screws. The deep six-lobe recess (also called a star drive) withstands more torque than slotted, Phillips, and hex drives.

Length is measured from under the head.