I'm trying to replace by bathroom sink drain, because I picked up a new faucet that included one with a new pop-up stopper, the old one isn't working anymore. The new faucet is already installed. I have removed the trap under the sink, and I'm trying to remove the big nut for the drain under the sink, but the whole drain keeps twisting. Am I supposed to hold it somehow? I briefly tried taking a hacksaw to it, but it doesn't seem to be cutting through very well. Any help or insight appreciated. Thank you