A Stick… 

150mm long made to fit your callipers so you can measure and calibrate your x and y stepper motor steps. 

Every printer is just a little different, if you calibrate properly you can use multiple printers to print larger multi-piece models and have them fit together! 

you could also use it for Z just need to turn it on end, and widen it up for stability in the slicer. 

let me know how far off your printers were :)