Releasing power of Mainspring (fusee clock shown above)
All clocks have a mainspring. You should note before taking any clock apart this may be wound up. Any attempt to dismantle without doing something about this will be damaging to the clock. Therefore you need to let down the power of the mainspring before you dismantle the clock. This is done by carefully and painstakingly by holding the winder, raising the click or pawl, and releasing the power gently until its all gone.
After this you will probably take off the hands and dial to dismantle the clock. The details explained above is known as the motion work and is distinct from the movement which is between the plates.