I'm putting in a new bathroom sink and when I try to tighten the large nut on the drain stem, the drain turns with it and leaks. I've tried to insert a screwdriver to stop the drain from rotating with the nut but can't hold it. Plier handles are too large for the drain as well. Any good ideas on what to use to stop the drain from rotating??

Call me... twizzled!

Once you have turned the drain in the sink your seal is pretty compromised. You should really remove the drain and put in new plumbers putty. You will have more luck keeping the drain from turning by holding the pipe from under the sink with a pair if vise grips, gouges will not show.

Thanks... I'm not worried about the gouges showing, just whether the vise grips will damage the threads so the large nut won't go back on/off. Thanks for the advice on compromising the seal too.

Put the vise grip on the smooth shaft of the drain pipe to hold it while you tighten the nut with a proper spanner. You won't be touching the threaded area of the pipe.

Okay.. thanks. I'll work with that. It's actually threaded all the way up the stem except for where it is hidden between the nut and the drain flange. You've given me enough to go on though, I think. :-)