Sample of tool usage is in last part of video.
3d printer bed level gauge.
Move your extruder to a corner and position the blade under the nozzle adjust the screw until the led will light up indicating that the tip of the nozzle is touching the feeler gauge blade repeat the process in the other corners until you find the perfect calibration.
This is all in one video of published bed leveling tool that i posted on thingiverese.
Connecting a multimeter in continuity mode causes a beep sound when the head is the correct distance.
To actually level the bed is really simple it just takes some practice to get it right.
Repeatable method of leveling a three dimensional printer bed by placing a feeler gauge thickness gauge blade between the extruder and the bed.
For 3d printer bed leveling and nozzle gap adjustment you ll need a card of a size you can comfortably hold and slide between the nozzle tip and the build plate.
A piece of ordinary office paper cut down to about 100 mm x 40 mm should work.
Home the z axis of your 3d printer.
Here is a good starting set of tools needed to maintain your bed level and nozzle gap.