As I recall, they used some kind of a little tiny nozzle that was hooked up to a hose or wire of some sort connected to a big machine, and basically, the nozzle was placed onto the wart, and pretty much felt like they were electrocuting my finger. Then for several days afterward, the wart looked like a big, bloody, dried up booger stuck to the side of my finger, and I had to just let it fall off little pieces at a time.