Class 3 (see Figures 7-8 and 7-9): The effort is located in
the middle of the lever and the load and the fulcrum at its
ends. Because of this arrangement, the class 3 levers have
a mechanical advantage of less than 1 and are used to
trade force for distance rather than the other way around.
This makes them useful when there is plenty of force
that can be used to move the load over greater distance.
Example: a boom of a crane elevated by a pneumatic
cylinder attached to its middle
Figure 7-8: Class 3 lever with the effort (green) in the middle and the fulcrum and load (red) at its ends