When aligning a cartridge for installation using the alignment protractor, it is important to remember that you are trying to align the cantilever (and therefore the stylus) and not the cartridge body. There is no guarantee that the cantilever (stylus) is perfectly aligned within the cartridge body, so simply aligning the cartridge body may not necessarily produce the desired result. Additionally, many cartridge bodies have non-parallel sides, making it virtually impossible to tangentially align the cartridge body with the contact lines of the gauge.