Bed leveling square plate test

To test how even oder uneven my bed is, I made this square plate.
I have watched some bed leveling videos, but none of them worked on an uneven bed, so I made this plate to test the bed.
With this plate you can also test your bed and level your bed.
As a result this video came out. I hope it helps some people.

https://www.youtube.com/watch?v=1f9R7coLKo4&list=PLDzmnDzv2yXUnJbJK8vdjdnQ_1GNot2Es