Stack Wires on a Shared Stud
Ordering ring terminals largest-to-smallest from the base, so no small terminal carries the current passing through it to a larger one.
Read a Lamp Cord's Polarity by Feel: Ribbed Is Neutral, Smooth Is Hot
Two-wire lamp and appliance cords look interchangeable, but they're marked — the conductor with the ribbed jacket is the neutral, the smooth one is the hot. Wiring them backward puts the switch and socket threads on the live side.
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The Problem
Rewire a lamp or swap a plug and you meet zip cord: two conductors, both insulated in the same brown or white jacket, no black-and-white color coding anywhere. It looks like it can't matter which wire goes where. It does — a lamp wired backward still lights, but the socket's threaded shell and the switch end up on the hot side, which means the exposed metal a fingertip can brush while changing a bulb is live.
The Technique
The cord is marked — by texture, not color:
- Run a fingernail across both conductors' jackets, or look closely under good light.
- One side has fine ribs or ridges molded along its length; the other is smooth.
- Ribbed is neutral. It connects to the wide prong of the plug and the silver screw — on a lamp socket, that's the threaded shell.
- Smooth is hot. It connects to the narrow prong and the brass screw — the socket's center contact, through the switch.
Wired that way, the switch interrupts the hot, and the threaded shell around the bulb sits at neutral — the arrangement every polarized plug exists to protect.
Pro tip: Some cords mark the neutral differently — a printed stripe, a thread tracer in the strands, or lettering on one side only — but ribbing is the overwhelming convention on ordinary zip cord. If you genuinely can't find any marking, the cord isn't polarized stock; replace it rather than guessing.
Safety note: Unplug before touching any lamp wiring — and treat the ribbed-neutral rule as how to wire it correctly, not proof it was wired correctly. On anything already assembled, verify with a tester before trusting exposed metal; the previous person may not have known the rule.
Electrical, plumbing, and structural work may be regulated where you live — check local code before you start, and note that a permit may be required. More in our disclaimer.
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