The empty slots on a sprue mark where you stopped

A grey plastic sprue frame, printed flat across the chest of a tee.

Fourteen or so parts still hang off it on thin runners, each with a small number moulded beside it.

Three positions are empty. Cut away, leaving a pale stub where a runner used to meet the frame.

A single letter, B, moulded small into one corner.

That's not artwork arranged to look technical. That's a parts list with some of the parts missing, because somebody used them.

What is a sprue, exactly?

The frame a plastic kit's parts are moulded onto, before anyone touches them with a blade.

Injection moulding makes many small parts in one shot, and the fastest way to keep them organised is to leave them attached to the tree of plastic that made them, connected by thin runners. A kit isn't sold as a box of loose pieces. It's sold as two or three of these frames, each one a self-contained inventory that hasn't been used yet.

Why are the parts numbered and lettered?

So a kit with three hundred pieces can be described in an instruction sheet with a single digit and a letter, rather than a description.

Part 14 on frame B means one specific shape, and nothing else on the kit needs to look like it. The numbering is what lets a build be broken into steps at all — the instruction sheet does the actual choreography, but it works because every part it's pointing at already has a name. A loose piece on a carpet is just plastic. A numbered one is part 14.

What does the stub where a part used to be actually show?

How it was removed, and by extension, who removed it.

A clean stub, cut close and flush, is nippers — someone who knew a blade drags plastic and tears the surface. A ragged one, pulled and twisted rather than cut, is a first kit or an impatient one. Neither is wrong. But the difference is visible for as long as the sprue survives, which is longer than most finished models do.

Is an unfinished kit actually worth putting on a shirt?

The unfinished one is the true version of the hobby, not the exception to it.

Most kits bought are not finished. They get carried a good way in — a wing, an undercarriage, the parts that were interesting to cut off and hold up to the light — and then something else happens: homework, a different kit, growing up. Three empty positions on a frame with eleven still full is a photograph of exactly that moment, more honest than a display case of the ones that got seen through to the end.

Do I need permission to put my own kit design on a shirt?

Not if the sprue is invented rather than a specific real kit.

The layout — parts on a frame, joined by runners, numbered and lettered — is a manufacturing method, not anyone's design. A real kit's exact part shapes, its box art and its model name belong to whoever tools and sells it, the same way a toy line belongs to whoever made it. Invent the parts and the letter and there's nothing to clear.

Does this work for something other than a model kit?

Anything that arrives as a set with a known count and gets used up piece by piece.

A dressmaking pattern with pieces cut from a sheet, a seed tray with some cells still full, a paint set with some pans scraped down to the tin — the format is any inventory a person worked their way through and then stopped. What carries across is the count: how many are gone tells the story better than a caption would.

Does it print well?

Yes, as long as the runners stay thin and the parts stay simple shapes.

Flat colour with hard edges survives fabric better than the fine moulding detail a real sprue has — the tiny ejector-pin marks and surface texture would fill in on cloth, so the print should simplify each part to its outline and let the frame's geometry carry it. Two greys, one a shade paler for the cut stubs, is close to what the plastic itself looks like anyway.

How do I get one made?

Describe the frame at JustOG — how many parts, which ones are gone, where the letter 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.

Somewhere there's a box with a sprue like that still in it, and nobody's coming back to finish it.