I also use it as flat on the ground as possible, and Its funny Dave should mention the jack rotation, I figured I was just improperly using the Jack, but couldn't figure out a way to rectify the jack rotation. As Dave mentioned the heels do tend to rust, So I wouldn't trust it to to much. I've always slipped axle stands underneath as soon as possible, just in case. I wouldn't trust this jack to support the cars weight even while changing a tire, I always set it down onto axle stands. Better safe then sorry. And remember (I'm sure we've all listen to this 1,000's of times), Never work under a car held up by a jack.