How to use the touch sensor

Hi guys!

I purchased a he3d k280 delta printer. Currently the printer is assembled but not calibrated. In the box with the printer there were 2 sensors, indicated in the manual as a touch sensor (see the photo in the attachment). I can not find anything about exactly how to use these things, because in all materials found by me, the calibration seems to be carried out without them. Can you please tell how to use these sensors, and is it necessary to use them for calibration?

maybe this video helps you