A system of keying implementation for swapping paired devices is provided. The system includes a controller module having a first keying member, a power supply unit having a second keying member, and a chassis having a plurality of receiving slots for receiving the controller module and the power supply unit. When the controller module and the power supply unit are a matched pair and when the controller module and the power supply unit are fully inserted, next to each other, into the plurality of receiving slots, the first keying member and the second keying member do not interfere with each other so that the power supply unit may supply power to the controller module.