Electric resistance welding is used to join two materials placed on top of each other. One use of this method is spot welding used to join, for example, steel plates.
The welding itself is achieved by the plates being sealed together by two electrodes. Electric current passes through these electrodes and since steel is a worse conductor than the copper electrodes, the passing current causes a great resistance which heats the surfaces of the plates being welded. This process takes place until both plates are physically joined. The created weld is characteristically very solid and resistant to sliding.