Packs of Metric Hexagon Steel Bolts & Set Screws For Motorcycles also available in Stainless. Historically the difference between a bolt and a screw was that the screw was threaded to the head whereas the bolt had a plain shank. However, this could cause you a problem if you made this assumption when specifying a fastener. The definition used by the Industrial Fastener Institute (IFI) is that screws are used with tapped holes and bolts are used with nuts.