Replace an electrical plug by cutting the old plug from the line, stripping the insulation from the wires and attaching the replacement. Unplug the cord from the outlet before beginning the task. As of 2015, the cost of the replacement parts is about $5.
Use wire cutters to remove the old plug, and thread the cord through the replacement. Use a utility knife to cut through and remove 3/4 inch of the outer jacket on the plug without cutting the inner insulation on the individual wires. Use wire strippers to remove 1/2 inch of insulation from each of the inner braided wires.
Connect the white wire to the silver screw, the black wire to the brass screw and the green wire to the green screw of the replacement plug. Attach the face plate to cover the wires over the plug prongs. If the replacement has a clamp to prevent strain on the cord connections, use a screwdriver to tighten it.
For an extension cord, use a plug-in circuit tester to check a three prong outlet. Then insert the new plug into the outlet and the tester into the opposite end of the cord. The lights on the tester indicate grounding and proper connections for the wires.