Bob,
Like Bill said in the first response. The light bulb socket has two contacts. The little round metal on the very bottom of the light bulb and the metal shell that is the base of the light bulb. The base should connect to the neutral of the 120V circuit and the little round metal on the bottom of the light bulb should connect to the hot wire of the 120V circuit. If the receptacle that you pluged the extension cord into has reverse polarity then the large metal base of the light bulb would be energized with 120 volts and that has potential for personnel injury.
That, computer equipment, and digital equipment need to have correct polarity. The light bulb would still work don't get me wrong. It's just dangerous. So would motors like your sawzall. But when it comes to computers and digital equipment, that is another story.
