A wire connector fastening tool comprises an elongate body having a first end, a second end, an outer hand-engaging surface and an interior surface. The outer hand-engaging surface has a generally uniform outside diameter from its first end to its second end. The interior surface defines an internal axial bore extending through the body from the first end to the second end. The axial bore has a first section with a first inside diameter and a second section with a second inside diameter. The second inside diameter is larger than the first inside diameter. The first section of the bore extends from the first end of the body to a point between the first and second ends of the body. The second section of the bore extends from the first section of the bore to the second end of the body. The first end of the body is adapted to engage with at least a portion of the first wire connector in a manner so that rotation of the body causes rotation of the first wire connector. The second end of the body is adapted to engage with at least a portion of a larger second wire connector in a manner so that rotation of the body causes rotation of the second wire connector. The internal axial bore is adapted to receive a pigtail or extension wire that extends beyond other electrical wires received in the wire connector. The pigtails and extension wires may be used for device terminations, and may be used as extensions for connecting the circuit to other circuits or electrical devices.