Plug with raised ribs provide non-slip gripping profile for turning to lock and unlock. Quick-thread assembly screws and cord-grip screws come backed-out, ready-to-wire. Industrial-strength, brass alloy plug blades and connector contacts resist heat rise, provide excellent conductivity. Double dovetail design provides superior protection against cord pull-out forces. Impact- and corrosion-resistant durable nylon 6/6 shell material. Rounded back contour reduces snags and hang-ups on the job site. Scallop shell design provides non-slip gripping surface for insertion and withdrawal. Integral flexible rubber cord grommet conforms to and seals around SO cord to provide protection from oils, water or chips entering wiring chamber.