The folder contains 4 different Bed Leveling files.
I placed 5 or 9 20x20 cubes perfectly aligned cubes in the files.
One plate / cube is always exactely in the middle, the rest are in the corners.
You can choose between 5 or 9 cubes and if they are 1mm or 10mm high.
I recommend writing numbers on top of the cubes after print, so you can tell where they were after you took them of the bed.
I used them to calibrate my Anet A8 after upgrading it with the Anycubic Ultrabase bed.
I recommend using SKIRT and no BRIM. That way you can compare the sharp edges of your objects.
Remember to put numbers on and take a photo before removing, so you can compare them with the next print run after leveling again.