XYZ Squareness (Lean) Test

Print this and measure across the diagonals. They should all be pretty close. (It's a truncated cube so that first layer mash doesn't confuse things, and your corner speed shouldn't be an issue.)

The dots tell you which face is X and Y. The hollowed out portion is intended to make it print quicker, but doesn't actually help all that much on low infill.

TODO: Write down what the corners *should* measure.