Different types of screwdrivers include Phillips head screwdrivers, slotted head screwdrivers, Posidriv screw drivers and square recess screw drivers. Other types include drivers designed for torx screws, hex nuts, tri-wing screws and spanners.
By far the most common type of screwdriver is the Phillips head screwdriver, followed closely by the slotted head screwdriver, which is older. The Phillips Screw Company and the American Screw Company designed the Pozidriv screw drive together, giving it four additional radial lines that make it more difficult for the driver to slip out while turning a screw. Pozidriv screws are more commonly used in Europe than in the United States.
Square recess screws offer better purchase and hold when driving screws; they are more difficult to damage accidentally. Torx screw drives are shaped like a star with six points, offering increased purchase and torque. Hex screws also have six points, but feature straight lines between them, giving the drive a hexagon shape. Hex screws are typically used in conjunction with Allen wrenches; many applications call for hex screwdrivers.
Tri-wing and spanner screwdrivers are notably less common than any of the other types. Tri-wing screw drives feature three slots that radiate outwards from a triangular center hole, and spanner screw drives feature two eyes that fasten to the screw drive, creating a tamper-proof seal.