Allows you to use a 10-32 screw has a fine adjustment for the RigidBot's z-stop switch. It should fit snuggly on the cylindrical protrusion from the bearing holder on the X-axis gantry. I prefer this method over adjusting the bed so that I can adjust the bed to level the bed and then adjust this to dial in the nozzle height. Use an M3 screw to attach it to the bearing holder. Use a 10-32 screw as the adjustment screw.