So they are very strong and roll like a dream. But this locking mechanism makes absolutely no sense. It's so stinky, hard to latch and you'll drop the 200lb thing holding it if you try to pull hard enough to unlock it. I had to ask another person to help me and use tools to get it back into the unlocked position. So. it really doesn't make any sense. And the lock feature was a big part of what I bought this for.