A screwdriver is a tool used to tighten or remove screws. Screwdrivers are identified by the kind of screws they fit. The commonest types of screwdrivers are the slotted (also known as straight-edge, flat, or standard tip) and the Phillips head. More specialized varieties include:

 

Allen or hex. This works with screws that can also be operated with Allen or hex keys. It is suitable for socket-head screws that are recessed.

Robertson or square. This has a square drive that gives high torque power and can reach screws that are sunk below the surface. Robertson screwdrivers are usually color coded according to size.

Clutch-drive. This has an hourglass-shaped tip that is especially useful when extra holding power is needed, as when working on cars or appliances.

Torx. This has a star-shaped tip that is useful for replacing such parts as tailgate lenses. It is widely used in automobile repair work. Torx screws are also used in household appliances, as well as lawn and garden equipment.

 

Some types of screw heads

 

A screwdriver is most effective when the width of its head matches the width of the slot in the head of the screw. Among the most generally useful screwdrivers are a quarter-inch slotted and a number two Phillips head. However, it is a good idea to have a complete set of screwdrivers to match the variety of jobs can crop up around the home and elsewhere.