During surveillance, you can check, unobserved, whether a vehicle has moved and returned to its usual parking space by using binoculars to note the positions of the valve stems on the wheels. Note the position of the stems and analogize them to clock-hand positions. For instance, the front tire could be at 3 o’clock and the rear tire at 6 o’clock. This could be noted as 3-6 or 3:30. The chances of the vehicle being driven and parked with the valve stems in the same position are extremely slim. The wheels of a car do move roughly in unison, but the valve stems change positions in relation to each other each time the car turns, parallel parks or hits a hole in the pavement. Try it in your parking lot with your own car and you will see that a single trip around the lot will throw the wheels out of sync.