I'm trying to replace my bathroom sink but I can't get the pipes apart. I can't get the "water trap nut" (I think that's what it's called... the big silver attaching piece) to loosen. There's a close up in the second picture of the piece I can't get apart. I have no idea what to or even which way to try to turn it. Every time I try to turn it just moves the pipe and I'm scared of it breaking... any advice?