The Original Prusa MK4/S, MK3.9/S, and XL are equipped with a loadcell. This component incorporated in the hotend heatsink detects if the nozzle is close enough to the steel sheet for printing.
The only adjustment needed for the loadcell is during the selftest. After that, the first layer calibration is always done automatically during the mesh bed leveling. This avoids any damage that would be caused by the nozzle digging into the steel sheet.
The manual first layer calibration (Live Z adjust) and the steel sheet profiles are not necessary with the loadcell, as the values are checked automatically before each print.
During the selftest, the loadcell will be tested: the printer will show the instructions for testing it.
Alternatively, the loadcell testing can be initiated in LCD Menu -> Control -> Calibration & Tests -> Loadcell Test.
During the test, you will be asked to tap the nozzle at a specific time, and a progress bar on top of the screen will be filled. If the bar is not filled or the printer shows any errors, please contact our customer support.