This thing is a tool designed to assist in physically levelling the heated bed prior to calibration using the bed fastening screws.

1. Place thing against a corner of the bed
2. Tighten the screw to lower that corner.
3. Loosen the screw to raise that corner.
4. When all corners of the heated bed are at the same height on the tool the heated bed is level relative to the printer platform.
5. Proceed with calibration as per the manual.