Flat head screwdrivers also known as slotted screwdrivers are the most common of all the screwdrivers and have a basic design that has been around for centuries. Flat head screwdrivers have a single blade with a straight flat tip that corresponds to the slot in the head of a slotted screw. Unlike Phillips or Torx screws slotted screws do not have a self-centering design therefore care has to be taken to align the screwdriver into the screw head to prevent ˈcam-outˈ or slipping. Torx screwdrivers are available in different sizes which indicates the width of the flat blade on the screwdriver tip.