This screw and nut set fastens the cutterbar knife sections to the knife head on the header of a grain harvester. It secures the knife section against the knife back, transmitting reciprocating motion from the drive to the cutting edge. A loose or missing fastener causes the knife section to shift, leading to uneven cut quality and potential damage to the knife head. The set includes the screw and its matching lock nut, sized for the original mounting holes in the assembly. On reinstallation, tighten the nut to the specified torque to prevent loosening under vibration.