It's usually presumed that there are three types of levers: the fulcrum in the middle, with the load on one end and the force at the other, and two others, with the fulcrum at the end, and the load and force alternating between the middle and remaining end. However, there is also a fourth lever, which has the force at one end and the load AT the fulcrum, which is moved by the applied force. To visualize this kind of lever, place your finger on the end of a strip of paper, then pull the other end straight upwards. This will pull your finger as the paper moves. A hinge can also be considered as being a moving fulcrum lever, with the sides referred to as leaves. However, the ends of the leaves must be pulled straight outwards, rather than be allowed to travel in a curved path. This is accomplished by building up momentum perpendicular to the direction of movement, then impacting the ends of the leaves. This produces a reaction which is perpendicular to the applied action. And this will also work while closing a hinge.