Although there aren't very many insulators in this postwar Americana scene, the ones that are in view are atop each of the street lamp poles. A spool insulator on each side of the pole is utilized to make deadend connections for the two wires leading to the light fixture. This was a street series circuit. In other installations with the same requirements, a special pole topper was affixed to the poletop with a metal pin in its center for terminating each wire (either by using a transposition or in-line guy wire insulator for making a "break" in the circuit). This was somewhat common practice through at least the 1950s where the street lighting wires ran overhead opposed to underground.