Whenever these threads pop up, I post the following that happened a few years ago as a warning...
A coworker of mine had his neighbor die while wrenching on his CRX. He was a certified Honda mechanic doing an axle swap in the driveway. He was using his brand new Snap On jackstands that have a round base and the theory is that they tilted and rotated. Here's a pic:
I agree with all those tips everyone else mentioned. Be careful out there guys!
Here's the e-mail from my coworker who was present just after:
My friends who work on "low to the ground" cars.
We had a very unfortunate event yesterday afternoon.
Our neighbor Mark across the street was a mechanic at Tipton Honda. He was out on his driveway working on his Honda CRX front suspension and changing axles. At some point the car came off the jack stands and landed on Mark's chest. We're not sure how long it was before he was discovered but we got word last night that it killed him, likely right away (massive internal damage - upper thorax).
I went over after the emergency response folks were gone to see if I could figure out what went wrong and take some photos. Mark had just purchased some new Blue Point jack stands and floor jack - very well built equipment. I noticed the base on the jack stands were made of a thick, circular steel plate unlike the usual 3 or 4 legged jack stands he'd been using for years and that most of us use.
It occurred to me that if he had been torquing on a large suspension bolt and got the jack stands to tip a little, their base would become a wheel and roll out from under their intended point of support with very little side load. Witness marks on the concrete support this theory. 2 arcing scribe marks in the driveway ending at the now tipped over jack stands (one had been moved before I got there - passenger side).
If you've heard of any problems with these stands (or had them yourself) be careful