This nut secures the straw-walker assembly to its drive shaft on the host combine. It is a threaded fastener, sized to match the shaft end, and its thread pitch corresponds to the original shaft thread. The nut maintains the correct axial position of the walker assembly, preventing drift during operation. A loose or improperly torqued nut allows the walker to shift, which can cause timing misalignment and increased vibration in the threshing unit. On reinstallation, clean the shaft threads and torque the nut to the specification for the assembly.