Azimuth Block. Place the protractor over the spindle so the grid lines up with your tonearm. Bonus Magnifier card, useful for lining up the stylus precisely on the protractor grid. Most turntables leave the factory without this being checked properly.
The Turntable Cartridge Alignment Setup Kit - Baerwald Protractor & Azimuth Block would be most suitable in a library, music studio, or music equipment repair shop where aligning record player cartridges is a regular task.
