Here a gfci receptacle is added at the end of a row of duplex receptacles for single-location protection. The first outlet is connected to the source and 2-wire cable runs from box to box. All wires are spliced with a pigtail at the devices to pass current from one to the next. The load terminals on the gfci are not used and it does not protect the other receptacles in the circuit.
Here one ground fault circuit interrupter protects multiple duplex receptacles coming after it, known as multiple-location protection. Two-wire cable runs from the gfci to all the following receptacles. The line terminals on the gfci are connected to the circuit source and the load terminals are connected with a pigtail splice to each of the following receptacles. This keeps each duplex connected directly to the gfci.
This diagram shows the wiring for multiple receptacles in an arrangement that connects each individually to the source. All wires are spliced to a pigtail which is connected to each device. This wiring allows for voltage at each device independent of the other outlets in the circuit.
In this diagram wall outlets are wired in a row using the terminal screws to pass voltage from one receptacle to the next. In this diagram, multiple receptacles are connected together using the device, instead of a pigtail splice as shown in the next diagram. Using this method, any break or malfunction at one outlet will likely cause all outlets that follow to fail as well.