Print this to test for mechanical backlash in your printer. It is also useful for verifying that you have properly compensated for backlash in your slicing software. As a bonus, you can test the dimensional accuracy of your printer without worrying about how backlash is affecting it. The dimension of the box should be 20mm, not including the "tabs" that stick out. It might be useful to scale in the X and Y dimensions to get better measurements.