When the bottom endstone of a Geneva cylinder watch is " fixed," it is set in a small plate of brass and held by a screw to the " chariot." To replace the fixed endstone by a loose one, push out the fixed stone from its setting, hollow out the setting from the inside a little with a round-faced chamfering tool, to cut away the sharp, rough edge, and pick out a loose endstone that will just lie flush in the hollow. Then place the loose endstone (shaped like a minute plano-convex lens) with its fiat on the jewel hole and the round side up. lay the small piece of flat brass over it, and screw it down as before. The brass plate will then hold the endstone tightly against the jewel hole. No cement of any kind is required.