This washer sits at the interface between a fastener and the threshing mechanism housing. It distributes clamping load over a wider area than a standard flat washer, preventing the fastener head from embedding into the casting. The integrated nose on the washer aligns with a corresponding recess in the mating part, keeping the washer from rotating during assembly or under vibration. A missing or incorrect washer can allow the fastener to loosen, leading to clearance changes in the threshing drum or concave adjustment. On reinstall, confirm the nose engages the locating slot and that the washer lies flat against the housing face.