These are the 4" solid concrete patio blocks and they are shimmed with the wood so you do not have the added force of the object dropping onto them to break them. But yes, they could still possibly crack and fall apart. The way I do it, I think the risk is small but it definitely is not zero. They are put there as an added safety to the jack stands. I also usually have solid 6 x 6 PT beams stacked under it too but they certainly would not prevent one from getting hurt (too easy to have the stack fall over) but they might save your life even if they do fall over. Even with all of that, I do my best not to get under the trailer etc and if I must, I minimize the part of me that is under the trailer and the time I spend under the trailer. I am a real wimp when it comes to working under loads. I still remember as a kid seeing the neighbor jack up his van by the front bumper and work with his head stuck over the top of the wheel. I thought he was nuts. He went into the house for something and the jack fell and the van crashed down. Wouldn't you know, he jacks it back up and does the same thing.
Ken
One of our patients was a former migrant farmworker, who had married a local girl, and had a couple of daughters, eventually becoming a citizen. They had been my family practice patients for 4 or 5 years and he was exactly the guy you'd want your son to turn out as- very hardworking, honest, generous to a fault, good humored, and completely devoted to his family until...
...He was trying to save money by working on his car that was up on a dept store floor jack like you saw at Kmart or Wallyworld all the time. No jack stands, no braces, or other safety devices, he was working alone in a basement garage where no one could hear him, and as best they were able to tell, the jack leaked out allowing the the car to sink down, trapping his head between the tire and the inside of the wheel well. The worst thing was, he may have been conscious for a large part of the night, but mercifully, he was unconscious when she found him in the morning.
They called it "closed head trauma", and (unfortunately) he "survived" after having been in a coma for a few months, but because of the brain damage, he has become a willful, angry, sexually obsessed 3 year old with the body of an adult man. His wife has the worst of it as he tries to grope her or worse in public, eats what and how much of anything he decides to- leading to cramps and diarrhea at best, and requiring locks on all the cupboards and refrigerator, as well as her having to lock the outside door from the inside, so he can't just go out and wander all night getting into even more trouble.
I had been treating her for PTSD (from finding him), depression, and anxiety with only minimal success until we found an adult daycare that could cope with him.
Thomas
