This mechanical stopwatch features 1/5 second, 60 minute register, 60 second sweep. The top button allows the user to start and stop the stopwatch. The side button allows the user to return stopwatch hand to zero when stopwatch is in a stopped position. Wind it up before timing Give a firm press to the top button, the timer starts. The top button should make a 'click' when fully pressed. Press again, it stops. You can start/stop it over again to accumulate the time. Press the side button to reset only when it stops.