I designed this object to test calibration accuracy and leveling of my just finished Portabee printer.
Base was uniform 2mm (i.e. level) and X and Y Bars were right on!

The Bar oriented in Z (vertical) however showed a problem with the PLA being too hot (and no fan on printer?). The plastic remained hot with the printhead, effectively, stationary at that point and flowed down before it had a chance to cool. I wasn't expecting to test the temperature(!) so this was an unexpected bonus in testing ;-)

Reducing extruder temp to 185C resulted in corners of the 'base' lifting off the print bed. Raising the extruder temp to 210C kept the base on the bed and resulted in the proper hight of the Z feature - however, it is evident I'll have to add a fan to the extruder to cool the extruded plastic and preserve the proper form under these ccnditions.