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.