Generally Sligh grandfather clock parts are custom made to suit the different types and makes of clocks. Most of the clocks are powered either by springs or weights. Energy is stored in the mainspring when it is wound up or when the key is tightened. The Sligh clocks have three weights : The weight on the right side which sounds the chimes, the hour gong is sounded by the left strike and the centre which is used for the time and the pendulum. All the parts work together in motion to give the correct time, along with the hourly chimes.