Levers are denominated as being either first-class, second-class or third-class levers. A lever is classified based on the position of the fulcrum in relation to the point of effort and the load. The fulcrum is the pivot point of a lever.
A first-class lever will have the fulcrum located between the effort and the load. This could be exactly in the middle or off-center. In second-class levers, the load is between the fulcrum and the effort. In third-class levers, the effort is between the load and the fulcrum.
Some examples of first-class levers are scissors, pliers and seesaws. In these types of levers, the greater the distance of the effort to the fulcrum compared to the load and the fulcrum, the greater the force of the effort will be amplified.
Examples of second-class levers include wheelbarrows, nut crackers and staplers. With the load being in between the force and the fulcrum, the result is that the force will always have to travel further to the pivot, creating a mechanical advantage.
Third-class levers include tweezers, fishing rods and tongs. With the effort being in the middle, the mechanical advantage that is drawn from the force in relation to the load will always be inferior.