Bolt is the long screw and Nut is the round one that goes on top of the Bolt right?
I am just going by what I am learning from you guys from your answers. The plumber said all I need is a Nut and no need to remove the toilet. Now the guy didn't properly look at the 2nd toilet, he gave a quick look after saying he doesn't have time . later today when I asked him why he ignored my concern on this 2nd toilet, he said all I need is Nut. I believe though not sure than rings and probably the flange is rotten and rusted once he removes the toilet and they may need replacement too.
Yes, the nut is the small hexagon fastener that threads on the closet bolt.
Why do you think the nut needs replacing?
John