This lock secures the tubular shaft of the tillage unit to prevent unintended rotation or disengagement during operation. It engages with the shaft coupling to maintain positive drive alignment between the gearbox output and the implement’s driveline. A worn or missing lock allows the shaft to slide axially, which can cause the drive to disengage or the PTO splines to wear unevenly. This component is manufactured to the original Sulky geometry so that the locking mechanism seats fully into the shaft groove without requiring shimming or modification.