The item is printed upside down and rotated at 45 degrees to enable it to fit on the build plate.

This jig is used when running the calibration script for a thing-o-matic with heated build platform.

Run the script and place the jig on the platform as in the photograph. Lower the extruder nozzle by turning the z axes rod by hand, while moving the platform in the x-y direction such that the nozzle lands in the cross in the inner circle.

The nozzle is now in the centre of the build platform. Rotate the z axes screw to raise the nozzle, remove the jig, lower the nozzle back to the build plate and set gap between nozzle andf plate with your usual calibration tool. ( I use an old business card).

Hope this is useful, I have been using it for a few months now.