I use a cheap, 1" long bubble level (not a round one, which would be pretty useless).
To compensate for the inaccuracies of a bubble level, if any, all you have to do is spin it 180 degrees and re-check on the same axis. If the results differ, halve the difference and you're level. Nothing could be simpler.
To compensate for the inaccuracies of a bubble level, if any, all you have to do is spin it 180 degrees and re-check on the same axis. If the results differ, halve the difference and you're level. Nothing could be simpler.