The hex head cap screw is a common fastener in construction and machine assembly. The screw head is designed to fit a ratchet or spanner torque wrenches allowing you to tighten the screw to your exact specifications. Hex head cap screws are typically used to create a bolted joint, in which a threaded shaft exactly fits a corresponding tapped hole or nut. Grade 2 screws tend to be used in construction for joining wood components. Grade 5 screws are used in small engines. Grade 8 screws provide high tensile strength.