Always use a driver bit of the proper size which is in good condition. Slotted Drive Accepts standard blade screwdriver. Requires less downward pressure to drive parts than those with recessed openings. Use proper fitting driver to minimize slippage. Hex Drive Accepts hex wrench.
Slotted drive is added to make it easier to remove the fastener.
Square Drive Increases productivity with excellent torque transmission and resists cam-out. Distinctive appearance which discourages tinkering.