Automotive mechanics inspect, service, and repair the engines, brakes, and other parts of cars, buses, and trucks. They also perform routine maintenance to prevent future breakdowns. Diagnosing problems quickly and accurately requires analytical ability. It also requires a thorough knowledge of cars' mechanical and electronic systems and competence with a variety of electronic tools, such as infrared engine analysers and computers. Many mechanics consider diagnosing hard-to-find problems to be one of their most challenging and satisfying duties. After locating the source of the malfunctions, mechanics often need to replace or repair faulty parts. Some mechanics specialise in particular kinds of repair, such as electrical or transmission problems. They usually work in special service shops. Most mechanics work in automobile dealerships, automobile repair shops, and gasoline service stations. Many others are employed by federal, state, and local government agencies; taxicab and automobile leasing companies; and other businesses that repair their own cars and trucks. Automobile manufacturers hire mechanics to make adjustments and repairs after cars come off the assembly line. Other mechanics work for large department stores that have facilities for servicing automobiles.