The lever mechanism of staplers and nailers is an internal system that multiplies the force applied by the user. Unlike simple models where the force of the hand pressing directly pushes on the staple, a tool with a lever mechanism works differently. By squeezing the handle, a strong internal spring is first stretched using a set of levers. This stretching requires considerably less force than is subsequently required to engage the staple. When the spring is fully extended, the mechanism releases it and the stored energy is transferred by shock to the striker, which drives the staple or nail into the material. This makes it easier to work with hard materials and also reduces hand fatigue during repetitive work, as the user does not have to exert as much pressure.