A torque wrench works the same as a ratchet or spanner. The keys work like a lever to transfer power to bolts or nuts. However, a torque wrench ensures a specific force that prevent the bolts or nuts from damaging. Thanks to a torque wrench you will not turn the nut or bolt too hard or too soft. The key indicates a warning client through a spring and ball. After this click the nut or bolt is tightened.