List of screw drives

A screw drive is a system used to turn a screw. At a minimum, it is a feature on the screw that allows torque to be applied to it. Usually, it also involves a mating tool, such as a screwdriver, that is used to turn it. The following heads are categorized based on commonality, with the less common drives being classified as "tamper-resistant".

Most heads come in a range of sizes, typically distinguished by a number, such as "Phillips #00" or "Torx T5." These sizes do not necessarily describe a particular dimension of the drive shape, but are often arbitrary designations in the same sense as a "Size 8" dress.

Common types

External types

External drives are characterized by a female tool and a male fastener

Square

Square This screw drive uses square fastener heads. They can be turned with an adjustable wrench, open-end wrench or 8- or 12-pointsockets. Common in the 19th and early 20th centuries, when it was easier and thriftier to manufacture than most other drives, it is less common today (although still easy to find) because the external hex is now cost-competitive and allows better access for wrenching despite nearby obstructions, with fewer degrees of swing on each stroke.