I know you have access to a pit, for which I am truly jealous, but all your pictures show the car up on a jack with no sign of an axle stand anywhere ..... and you are obviously "under" the car to take the pictures..... and we now know you had a problem with the car moving on your blocks of wood ....
I have lost a friend to a car falling off a jack onto him, and my brother, when a copper, had to attend at least two fatalities due to the same occurrence.
PLEASE, PLEASE, PLEASE do not work on a car supported only by a jack, it can only lead to trouble ...
Point taken. On this particular job I was jacking at the only obvious point for a jack. If doing any work under the car I also put an axle stand beneath the rear suspension, but for photographs I saw no point, as I was never under the car, but in the pit behind the car.
I have seen AA men working on cars supported only by trolley jacks, and commented, only to be told that 'it's a self locking jack, so OK'. Axle stands too can be hazardous, a car on only 4 axle stands is lethal. Wheels are best, I did most of this job with four wheels on the car.
In my first works safety course the instructor said 'You are your own safety officer. Always imagine what might go wrong, and make sure if it does it does not injure you'. I hope I still do that.
John Cleese was discussing on the radio how people worry too much. He commented 'get into a car driven by a man who never worries, you will soon appreciate your mistake'.