An externally threaded fastener whose external threaded portion is of one nominal diameter. it has a concentric hole along the longitudinal centerline which may extend a part or the full length of the bolt. the concentric hole along the centerline may be counterbored and/or internally threaded at the head end or the bolt end. the head is designed to be held or driven by an external and/or internal driver. for items having a hole(s) perpendicular to the axis which meet the concentric hole along the longitudinal centerline, see bolt, fluid passage.