Not always possible, and if that is the case, turn brain on and think first and don't take short cutsScreaming for help is hard to do if you can't breathe.. always have a buddy.. like swimming.
Jeez... What are friends for, right?I remember back in the 70's, working on my first car, a 67 MG Midget, I would use plastic milk crates as jack stands. One summer day, a fellow MG owner was there helping me by handing me tools while I was under the car. After I came out for a breather, his dog crawled under the car for a cool respite. He immediately called for the dog to come out from under the car. I asked him why he did that. He replied that it wasn't safe.