Simple X-Y Calibration

I've seen several X-Y tests but I created this to simply have a reference when changing the offset settings in Configuration.h.

I used a black magic marker to find the true center of my print bed.
I would then print an X to see how far off my print nozzle was.

It simply prints an 'X' on the bed where the current settings have it centered.
The 'X' is 5mm x .5mm tall and only takes about 10 seconds to print.
I adjusted the offset settings in Arduino and uploaded to the printer to check to see the results.