HeyBub wrote:
Bill wrote:

It seems if you were installing anything that has to do with water
(bath, kitchen, a boat)
then you would desire certain surfaces to be level. (To me), it
seems that anything
else should follow the wall or ceiling lines or be balanced in
between them.

Not always. If a bathtub or shower pan or drainboard (do they call
them that any more?) should or could have a slope to facilitate
run-off.

My tub had a slope the wrong way when I bought the house. Rotted out quite
a lot before I finally figured out what the problem was and fixed it.