This card of 0.3 mm thickness is used to adjust the distance nozzle - printbed and for printbed leveling: The bases of a good 3D print.

Usage:
Heat up the nozzle till printing temperature and extrude some filament. On each calibration point the metal card should be moved with a light / minimum of resistance between teh heated nozzle and the printbed. Repeat these steps and your printbed is leveled.

Use in your slicer the Z-adjustment / Z-hub / Z-offset (depending on your slicer and printer) to detirmine the right hight for a good print . We use this test for it. * Don't forget to alter the Z-height of the object in "Scale" from 0.20 mm to 0.21 mm height.