Safety First

What's he on about? you may ask.

The client here is very safety conscious and there is expectation that the philosophy extends to their site visitors.

I am parked on a slight slope. The handbrake is on and the car is in gear (or park position for autos).  There is still the possibility that both those standard precautions may fail so the driver is obliged to place a convenient brick in front of the wheel to prevent it rolling off down the slope and causing an accident.