Let it soak overnight with WD-40 or penetrating oil.
Then try to tighten it clockwise to try to break it loose, and then unscrew it counter-clockwise.
Good Luck!
When turning on the shower the nob turns and turns several times before and water comes. Then some times when turning the water off, it will not go off. At this point I use a screw driver to titen the center screw on the nob.
We are replacing an existing metal shower with a fiberglass shower. We have the same size as the old but need help on the drain. What do we need to do to make sure the drain matches the new shower and what needs to be done.