- ''This page is about tools, you might be looking for a type of cocktail, if so, please see screwdriver cocktail.
A typical flat head manual screwdriver.
A Phillips head screwdriver.
Screwdrivers come in a large variety of sizes to match those of screws, from tiny jeweller's screwdrivers up. It is important to use a screwdriver that is the right size and type for the screw used, or it is likely that the screw will be damaged in the process of inserting it. When tightening a screw with force, it is important to press the head hard into the screw, again to avoid damaging the screw.
Many screwdriver designs have a handle with detachable head (the part of the screwdriver in contact with the screw), allowing a set of one handle and several heads to be used for a variety of screw sizes and types. This kind of design has allowed the development of electrically-powered screwdrivers, which as the name suggests use an electric motor to rotate the bit, some drills can also be fitted with screwdriver heads. Manual screw drivers with mechanisms to turn pressure into rotational motion also exist, and predate electric screwdrivers.
Many contemporary electrical appliances, if they use screws at all, use Torx screws with oddly-shaped heads in an attempt to prevent users of the device disassembling them - see the article on screws for details. However, screwdrivers specifically designed for these special screws have become widely available in electronics stores.