...But I recond most of us, especily us oldes have done some thing daft in our past...
Oh yes. And mine involves a car as well. And it was using jacks as well.
I was doing some work on my mum's Triumph Herald. I had jacked the car up with the manufacturer's supplied screw jack and I was working on the front suspension. I had taken the wheel off and was sitting on the ground with my legs either side of the suspension when the screw jack wobbled and collapsed. Fortunately the jack fell backwards and I ended up with the suspension crashing to the floor with just enough clearance for my legs.
The car ended up leaning against the wall.
I've had that happen too. The jack under the car I was working on groaned and then the car slumped against the wall. This actually stopped it hitting the ground so was easy enough to jack up again.
Later on I discovered axle stands.