I didn't invent these Knob Lock doohickeys, but I made them purple so they match the Black Spiral. Simply remove your knob, place the Knob Lock over the potentiometer shaft, put the knob back on, press down and retighten. And like magic (or friction), the knob is held in place at your favorite setting. Set of 4 Knob Locks designed to fit the Black Spiral Fuzz (3 large, 1 small).