Bed level and Z offset test to make easy on the fly changes. I found with the level tests that print shapes in the 4 corners of the bed too difficult to see to make accurate adjustments before the print moves onto the next corner. This test prints a continuous stripe across the entire bed back and forth to identify any warpage or level issues so it's easy to make instant Z offset or level wheel changes. As simple as this design is i've found it more difficult to print perfectly than most of the corner print tests. Make sure that your slicer starts the print at the beginning of the stripe and not half way through