# A schematic is a promise that it's correct

> Trade merchandise defaults to a cartoon tool and a pun. A working circuit diagram says something a pun can't — that the person wearing it can be trusted with the wiring.

August 17, 2026 · https://justog.club/stories/electrician-trade-shirt

A two-way lighting circuit: two switches, a lamp, the travellers between them, terminals labelled,
a legend along the bottom.

To most people it's an attractive diagram. To an electrician it's a thing that's either right or
wrong, and this one is right.

## Why does correctness matter here?

Because it's the entire claim the design is making.

A cartoon plug with a face says *I do electrics*. A correct schematic says *I know how this
works*, and — crucially — a wrong one says the opposite very loudly to exactly the audience you
wanted to impress.

That's the risk and the appeal. This is a design that can be marked, and trades notice.

## What are the components?

Five, all standard drafting.

- **Standard symbols** — the ones the trade actually uses, not decorative approximations.
- **Junction dots** where conductors connect and hops where they cross.
- **Labelled terminals**: L1, L2, COM.
- **Line weight distinguishing** live, neutral and earth.
- **A legend strip** explaining the line types.

The legend is the detail that makes it read as a real drawing rather than as an illustration of
one. It's the same device as
[a figure number on a technical plate](/stories/fathers-day-custom-shirt): a small piece
of documentation apparatus implying the rest.

## Which circuit should it be?

One with a story in the trade.

A two-way switch is the classic — it's the first thing that confuses an apprentice and the thing
homeowners get wrong. Others with the same quality: a ring final, a motor starter, a three-phase
supply, a shower circuit, a consumer unit layout.

The best choice is whichever one the wearer has explained to somebody twenty times. That's the
circuit that means something.

## Does this work for other trades?

Directly, and the format transfers cleanly.

Plumbing has isometric pipe runs. Refrigeration has cycle diagrams. Networking has topology
drawings. Structural has load paths. HVAC has duct schematics. Every trade has a drawing convention
that its people read fluently and everybody else finds decorative.

That's the general form of this whole batch: **print the document, not the tool.**

## Can I put my company on it?

Small, and only if it's yours.

A sole trader's own mark on the sleeve or under the diagram works well — it turns the shirt into
[a staff shirt](/stories/small-business-staff-shirts) that people will actually wear, which is
rare. Use the
[one-colour version](/stories/company-logo-on-a-shirt).

Somebody else's employer logo isn't yours to print, and a manufacturer's brand on the diagram is
the same issue in miniature. Keep the symbols generic.

## Does it print well?

Very — it's flat line with hard edges and good spacing.

The risk is the labels. Terminal markings and legend text at real drafting scale drop below
[the weave's floor](/stories/bold-shapes-survive-fabric), so they need to be larger than a
real drawing would set them, and there should be fewer of them.

Keep the circuit itself at full complexity and thin out the annotation. The diagram is the design;
the text is the caption.

## Is there a joke version?

There is, and it's a good one: a schematic for something that isn't a circuit.

A wiring diagram for a household argument. A three-phase supply feeding a kettle. A fault-finding
flowchart that terminates at *turn it off and on*. The drafting conventions carry all of the
seriousness, so the subject can be anything —
[the same trick the instruction sheet makes](/stories/mecha-instruction-manual-style).

## How do I get one made?

Describe the circuit at [JustOG](/) — which one, and whether it should be straight or a joke. Pick
a direction, drag the crop frame, see it composited on the real garment, and it's made to order
and shipped.

Designs other people have published are in the [shop](/shop).

Anyone can wear a picture of a plug. Not everyone can wear a diagram that's right.