Dial Mount for Prusa i3 MK 1 2 etc

thingiverse

Level out the printer's surface by disabling the motors. Securely attach a clip to your extruder motor. Gradually lower the X-axis until it reaches a reading on one corner, then set that point as zero reference. Move the print head to each of the four corners in turn and fine-tune the bed height to match on all four corners. Finally, check the middle of the bed for any signs of warping.