The slotted style is the original type of screw drive, with a straight slotted line going across the screw head, from end to end. These are also very common, though it is becoming harder to find them in applications that require a good amount of torque because the screwdriver tends to slip out of the slot more easily than drivers do for other screw drive types. Slotted screwdrivers have a flat blade that varies in size depending upon the size of the slot.
Phillips is perhaps the most common type of screw drive. It is characterized by a cross in the middle of the screw head, with the four ends not extending to the end of the screw head. The cross also has a ball point in the middle. The screwdriver itself is cross-shaped, with each cross blade being tapered at 57 degrees. Phillips screw drives come in a range of sizes, the Phillips #2 is perhaps the most commonly used Phillips screw drive.
The Pozidriv screw drive is actually an enhanced version of the original Phillips drive. Developed by the Phillips Screw Company and the American Screw Company, the recessed flanks of the Pozidriv screw drive are not angled upward like the Phillips drive is. There are also four additional recessed radial lines, with one in between each of the main recessed flanks that form the cross on the screw head. These radial lines are shallow, but they do create additional contact points. These extra contact points, along with the right angles on the recessed flanks of the cross, make it more difficult for a Pozidriv screwdriver to slip out while turning the screw. This in turn allows for more torque to be applied. Pozidriv screws tend to be used more in Europe than in the United States, and the three most common sizes are #1, #2, and #3.
External drivers for hexagon bolts and nuts come in many types and sizes. There are open ended spanners, ring spanners, adjustable spanners/wrench (also known as a shifter) and socket drivers which can be attached to a variety of handles which offer torque, speed, accuracy and flexibility.
Hex Key / Allen Key
A hex key or Allen key is a tool of hexagonal cross-section used to drive bolts and screws that have a hexagonal socket in the head (internal-wrenching hexagon drive). Also available as a screwdriver, T handle driver & socket wrench.