I personally will never (never say never) put myself under a car with just a jack holding it. I used to but quite a few years ago an acquaintance of mine was in his yard working on a trailer with just a jack under the axle when the jack popped out from under. They figure he was under the trailer for about an hour before the wife came out to call him for dinner. It was too late. You would think I would have learned that lesson before that accident. I was changing a front tire on a 55 Studie one afternoon with just a bumper jack, I got the old wheel and tire off and was sitting on the ground with my legs under the car putting the spare on when the jack popped off the bumper. I had just gotten the wheel on and had taken one turn on first the lug nut when it popped off. That was one of my many lucky days. Any way, never again.

Jack.