These call for no special remarks, beyond that it is advisable to well understand the action of the "letting off" work, and the "run" allowed, before taking to pieces. The arrangements are so different that scarcely 2 are exactly alike; but they seldom offer any great difficulty when ordinary care is taken. It is wise in some cases to keep the striking and chime parts distinct while cleaning. Most of these clocks present favourable points for improvement by reducing the friction, and, when it can be safely done, it is well to do it; for, though the weights are unusually heavy, there is generally no power to spare.