Quadrex
A screw drive is a system used to turn a screw. At a minimum, it is a set of shaped cavities and protrusions on the screw head 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 some of 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.
The slot screw drive has a single slot in the fastener head and is driven by a "common blade" or flat-bladed screwdriver. It was the first type of screw drive to be developed, and for centuries it was the simplest and cheapest to make. Uniquely among common drives, it is straightforward to manufacture a slot head or drive by hand. The slotted screw is commonly found in existing products and installations, and is still used in some simple carpentry, and applications where little torque is needed. It is used in restoration of old and antique furniture, vehicles and equipment. However, it is not well suited to installation with power tools, because a power driver tends to slip out of the head, potentially damaging the screw and surrounding material. For this reason, cruciform and other drives have replaced it in most applications. The tool used to drive a slot is called a common blade, flat-blade, slot-head, flat-tip or flat-head / flathead screwdriver. A hollow-ground screwdriver is less likely to "cam out" (leave the slot due to torque being translated into an axial force), so more torque can be applied without damaging the screw head. Flat-blade jewelers' screwdrivers and the tips found in 1⁄4-inch drive sets are generally hollow-ground.
Coin-slot drives are so-called because of the curved bottom of the recess that facilitates driving them with a suitable coin, are often used on items where the user is not likely to have a screwdriver when needed, such as on thumb-screws that attach cameras to tripod adapters and battery compartments in some equipment.
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