Thing-o-matic calibration jig.
thingiverse
To use the jig during calibration for a Thing-O-Matic with a heated build platform, place the nozzle in the center of the inner circle's cross. Invert and rotate your item 45 degrees to fit on the plate. Run the script and follow the steps: adjust the z-axis rod, move the platform, remove the jig, and set the nozzle gap with a calibration tool. This method has been effective for me over several months.
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