Does X chocks help stablity?

I have the pair of these. They take a lot of shake out of the trailer when locked in. I have heard (read) a couple people say that they don't stop the trailer from pulling away. I have never tugged on the trailer with them installed, but I can't imagine it moving anywhere. I guess if you really pulled it, they would let loose, but I would think it would take quite a tug. They really stabilize the trailer while set up.

BTW, If you get really interested, you can beat that price at PPL.