seniorgeezer wrote:
If you look at a long level there are usually two "bubbles", side by
side ... one concave up and the other concave down. I have always read
the one that is concave up in any application. No one at Home Depot or
Lowes home improvement stores seems to know the difference. Would you
please explain the difference, and which to use?

One is for use in the northern hemisphere and the other for use in the
southern. Do _not_ confuse the two or you'll find your building is
negatively level.

R