Good advice. As a sobering thought, have you ever wondered how close you may have come to being killed with not ever realizing it, wether it be by something you did or someone else's actions? Scary heh?
I had my Ramcharger roll off a jack one time, lucky it only squashed my finger, not something more vital. I now use redundant after redundant when working under a car. Why does it take an accident for us to realize we need to work safer? ::
Had a friend killed in high school while working under his car while it was supported by a jack (the old bumper jacks). The car rolled, the jack kicked out and he was crushed by the rear landing on his chest.
That is the #1 reason why I own so many jackstands and wheel chocks ever since. Have never even been close to that kind of accident.