This spring washer provides preload tension at the fastening point within the tractor body structure. It sits between the bolt head or nut and the mounting surface, applying a controlled clamping force that resists loosening from vibration and thermal cycling. When the washer loses its spring rate, the fastener can back off, leading to rattling panels or loosened body components. The original manufacturer machines the washer to the same free height and load-deflection curve as the original assembly, so the clamping force matches the design specification. On reinstallation, inspect the washer for permanent set and replace if it has flattened.