On Saturday, December 30, 2017 at 2:37:48 PM UTC-8, wrote:

Just put it on something level (e.g. another level), then flip the
level end for end and top for bottom. If it doesn't read level after
any of the steps, throw it as far as possible and start over (with
another level).

Or, adjust it (for old levels, with replaceable vials, this was always possible).
Nowadays, the adjustment feature is sometimes absent.

Many manufactured items look 'fixed' though a litle hot vinegar would
dissolve the matrix around the vial, and allow adjust/replacement. Every
bent old level is a source of replacement vials when one cracks...