What are the applications of decade resistance box?

A decade resistance box is piece of laboratory equipment that allows the user to dial in a precise amount of electrical resistance to be inserted into a circuit. For example, it might have a dial for 100s of Ohms, 10s of Ohms, and 1s of Ohms, and allow the user to set any value from 999 Ohms to 0 Ohms in 1 ohm steps. While the use of this device has probably been largely superseded in laboratory use by more sophisticated equipment, it was used in the past in some or all of the following applications: Measurement of unknown resistances by the "bridge" method, Setting the current in a test circuit, Calibrating other lab equipment such as an Ohmmeter or Ammeter, Demonstrating Ohm's Law, and so on.