Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4389692.

Simple 100x100mm square for printer calibration and bed levelling. Used this to calibrate the X and Y scale on a new printer. It's quite minimal and a quick print, doesn't use much filament. One corner has a small triangle feature (i.e. so you can still identify the X and Y axes after removing the print from the bed...)

The lines are 1.6mm wide and 0.8mm in height.