The crosses on a compatibility chart are about money

Six component names down the side, the same six across the top. Where a row meets its own column, an amber tick. Elsewhere: ticks, half-circles for PARTIAL, and scarlet crosses for DO NOT PAIR. One cell carries a warning triangle. A legend at the base explains the symbols nobody needed explained.

Read the crosses as physics and the chart is boring. Read them as commercial hostility and it's the most honest document in the genre.

What is a compatibility chart actually showing?

A grid of which parts talk to which other parts, and which refuse.

Two components from two different manufacturers usually could work together — the underlying standard exists, the connector fits, the signal is a signal. A cross on the chart most often means a company chose not to certify the pairing, not that the pairing fails. Engineering explains the tick marks. Everything else on the sheet is explained by who owns whom.

The diagonal is the one row that's never interesting: a part is always compatible with itself. Everything worth reading is off it.

Why does the diagonal matter?

Because it's the only cell on the chart that mechanism decided rather than ownership.

Every other cell is a claim somebody made about a product they sell, evaluated by the people who sell it. The diagonal is the control — the one comparison with no commercial stake, since a part obviously pairs with itself. Once a reader has that fixed point, the rest of the grid reads differently: not as a report but as a negotiating position, printed in a font that looks like a report.

A PARTIAL mark usually means "works, with a warning label attached so we're not liable for it."

What makes a good version of this design?

A plausible taxonomy and a grid dense enough to reward reading.

Six items is the right count — few enough to hold in the eye at once, many enough that the pattern of crosses forms clusters rather than scattering randomly. The clusters are the joke: a reader should be able to look at the chart and guess which two names are owned by the same company, purely from which cells never carry a cross.

The one warning triangle

Every chart in this style earns one cell that breaks the pattern — not a cross, a triangle. It's the pairing that technically works and shouldn't be attempted, the cell somebody tried once and wrote the manual entry about afterwards. One triangle carries more weight than a whole row of crosses, because a cross is a business decision and a triangle is a story.

Can I use real product names on the chart?

Invent the six. Real brand names, model numbers and connector standards belong to the companies that made them, and a chart accusing a named competitor of deliberate incompatibility is a specific kind of claim a shirt shouldn't be making on someone's behalf.

None of that is a loss. Invented names are funnier here, because the reader supplies the real target from their own charger drawer, and an invented chart can be exactly as petty as the joke needs without anyone's lawyers getting involved. The style of a compatibility grid has no owner — the format is the joke, not the parts inside it.

Does this work for anything besides limb augments?

The chart doesn't care what the six things are.

Chargers, printer cartridges, coffee pods, game controllers, kitchen appliance attachments — any category with vendor lock-in produces the same grid with the same commercial logic, and pointing the format at something completely mundane is often funnier than pointing it at the fictional hardware it was built for. A coffee machine that refuses a rival pod isn't solving an engineering problem either.

The mechanism reads the same whether the six rows are cybernetic forearms or milk frothers.

What's the strongest objection to a chart like this?

That it looks like a spreadsheet, and a spreadsheet on a shirt sounds like a bad idea.

It would be, printed straight. What survives the trip to fabric is the shape of the thing — a grid, a legend, a run of small symbols — not the fine print of an actual technical document. Treated as graphic design rather than data entry, a matrix is one of the more satisfying shapes to print, because flat cells with hard edges are exactly what fabric wants.

Does it print well?

Yes, with the symbol count kept short.

Three symbols — tick, half-circle, cross — plus one triangle is enough vocabulary for the eye to sort at a glance and few enough to survive at chest scale without turning to noise. The grid lines themselves want to be a single flat colour, not a gradient rule, or they go soft and grey on cotton. Slate, charcoal or a deep navy ground suits it, with the amber and scarlet as the only two accent inks and the tick marks in a third, quieter tone.

Six rows by six columns is close to the ceiling before the cell labels have to shrink past the point where cotton can hold them.

How do I get one made?

Describe the matrix at JustOG — the six names, which cells cross out, and where the one triangle sits. 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.

Two parts that would work fine together, refusing each other by design.