Additionally, it is unique because the slot head is straightforward to manufacture, and because it can be driven by a simple handtool. This form was the first type of screw drive to be developed, and for centuries, it was the simplest and cheapest to make because it can just be sawed or filed. Slot screw drives have a single horizontal indentation (the slot) in the fastener head and is driven by a 'common blade' or flat-bladed screwdriver. Standard slot screwdriver sizes (ISO 2380).

Slotted drives Slot drive tool and screw sizes Blade width