You no longer have to be the last one to meander down the path with your keys while everyone is waiting for you :-) It's very easy to use. Simply remove the caps from the valves (if any) and screw them on. After screwing it starts to drain immediately. Install all four tires, then go back to the first tire and start monitoring the pressure with the pressure gauge. When you get the pressure you want (eg 18psi in my case) unscrew it and move on to the next tire, measure, unscrew it, then the next tire and so on. Yes, these deflators will NOT stop at a certain psi pressure. This is better for me as I can choose how much to deflate and I don't have to worry about faulty deflators that can keep deflating. It's always best to have a pressure gauge with you and keep an eye on the pressure as you deflate.