A wrench's main function is to hold and turn nuts, bolts, caps, screws, plugs and various threaded parts. Applying excessive torque will strip or damage those threads, so quality wrenches are designed to keep leverage and intended load in safe balance. Wrenches can be classified as general use or plumbing wrenches. Top-quality wrenches are forged from finegrade tool steel, machined to close tolerances, hardened and tempered for long service life. Most types are sold individually and in sets of various sizes. Because most imported products are made to metric specifications, a set of metric wrenches has become a must in many home workshops.
Users should not put "cheaters" on wrenches to increase leverage. The proper size wrench should be used. Too large a reach will spread the jaws of an open-end wrench or damage the points of a box or socket wrench. When possible, a wrench should be pulled, not pushed.