It's roofs.

I seem to remember an earlier thread on ice dams, and Barry Finn wrote a song about the slippery work of getting rid of them. I didn't think about the panty hose. I just filled up a sock, tied a string on, threw it on the roof and pulled it until it was on the ice. I moved it after a while. I've never had any back-up, but the dam I had forming made me think it could happen.