It is crucial to use the proper amount of torque when tightening nuts or cap screws on any part of a vehicle, Particularly the engine. A torque-indicating wrench make it possible to duplicate the condition tightness and stress recommended by the manufacturer Metric and SAE size Wrenches are not interchange able. An auto technician should have a variety of both types.A screwdriver, no matter what type, should never be used as a chisel, punch, or pry bar. The hand tap is used for hand cutting internal threads and for cleaning and restoring previously cut threads. Hand-threading dies cut external threads and fit into holders called die stocks. Carelessness or mishandling of power tools can cause serious injury. Safety measures are needed when Working with such tools as impact and air ratchet Wrenches, blowguns, bench grinders, lifts, hoists, and hydraulic presses. The primary source of repair and specification information for any vehicle is the manufacturers service manual. Updates are published as service bulletins and include changes made during the model year, which will not appear in the manual until the following year. Flat-rate manuals are ideal for making cost estimates. Published by manufacturers and independent companies, they contain figures showing how long specific repairs should take to complete, as well as a list of the necessary parts and their prices.