Before revision: 250px|Wheel chocks placed around an aircraft's landing gear Wheel chocks (or chocks) are wedges of sturdy material placed closely against a vehicle's wheels to prevent accidental movement.
After revision: Aldon Company railroad wheel chock installed under gondola railcar250px|Wheel chocks placed around an aircraft's landing gear Wheel chocks (or chocks) are wedges of sturdy material placed closely against a vehicle's wheels to prevent accidental movement.