Pretty much self explanatory. I like a very small gap. It's about 1mm and very sensitive. The lower contact is wired in a groove under the clothespin. The upper contact is wired into a groove on the top of the clothespin. The screw on the pinchy end adjusts the gap and also the tip of it fits into the crosshead of the screw under it that holds the pin to the base. That keeps the clothespin from slipping to the sides.