ezra, the way that many of the trailers were set up, was with a compression fitting for the tie down nut. So the sleeve was pressed together and that held it in place. The replacement parts are the blocks you are talking about, with the C clips. So, over time, the vibration and wear just lossen up the sleeves and they begin to spin in place. The only thing I don't like about the block and C clip, is that if that C clip breaks, you'll lose the block. And, they sit up off the deck a little, so if you are shoveling snow off, you catch them with the edge. But that's not a reason to avoid the trailers.