decades hundreds thousands of years people have been using spirit levels, but they have a problem, they don’t contain enough technology. Instead of using this, you can now use the Action Level Cross (Warning: Bizarre website that needs IE).
Instead of always-on, always-ready old-school technology you can have press-a-button-and-wait-two-seconds technology, which requires batteries, and a manual, and is probably hard to see in bright sunlight. If you still want one, they’re £44.95 from Amazon UK
A multifunctional and clever Action Level model prevents slant pictures conveniently. The custom zero point setting adjusts coordinate axis according to each camera’s specific position.