Ender 3 runout detection switch holder

I based my design on a thing by markj113. The switch is flipped to the other side to accommodate a ball bearing filament guide.

This fits a standard KW3 microswitch with a long roller arm.

Runout detection can be wired into pin 27 or pin 29 on the mainboard.

You will need a small amount of PTFE tube in order to provide a smooth filament path.