A torque wrench is a tool that allows one to control circular force, or torque, when putting in, removing or tightening a bolt or a nut. It comes in many different styles and levels of complexity depending upon its applications.
A simple one, called a beam torque wrench, has a scale on the wrench that will measure the amount of torque being used. The scale is attached to a slightly flexible arm that will show the scale of torque when the wrench is in use. This type may be okay for general use, but it tends to be somewhat inaccurate in its measurements. When one must very specifically measure the amount of torque, using the simple torque wrench is inadvisable.
Another type in quite common use is called a click torque wrench. Prior to using the wrench, one can set it to provide a specific amount of torque and no more. When the amount of torque needed is reached, the wrench mechanism slips so that no more force can be applied.
Click torque wrenches are typically used to tighten bolts on the wheels of cars. Too much torque can strip the metal holding the bolt, and cause the wheel to become loose. This tool may also be used to fasten roof bolts, bolts on bicycles, and in any application where nuts and bolts need to be tightened.
The torque wrench can vary greatly in price. The beam type is usually much lower in price, but may be a poor option where one requires accuracy in torque. A fairly well made click torque wrench comes at a higher price, which can vary depending on the size of the wrench required. People may also have sets of wrenches since not all nuts and bolts measure the same. For example, someone purchasing a torque wrench for a bicycle would want a much smaller diameter measurement fitting than a person purchasing one to tighten roof bolts.