Minimal bed leveling test

Minimal but comprehensive test for bed leveling verifying proper adhesion.
The Xs are 15mm high and 15mm wide, and are orthogonally 15cm apart.
It tests each corner and the center.
The fourth corner test would have been superfluous.

The marks are just wide enough to check in-layer cohesion and just tall enough cross-layer adhesion.

Print without skirt or brim.