In testing a lever clock hairspring by counting its vibrations, fix it temporarily to the balance, and with a pair of tweezers hold the outer end of the spring in such a way as to let the bottom pivot of the balance rest on a watch glass on the hoard. The spring should be drawn up into a spiral, letting the weight of the balance hang upon it, so that there is hardly any weight resting on the bottom pivot. In this position a turn of the wrist will start the balance spinning, and it will continue for some time, enabling the vibrations to be counted for a full minute if necessary.