A crash-lock, or auto-bottom, carton is a folding box that opens into a locked base. What carries the product is a path: the goods sit on overlapping flaps, the flaps meet the side and end walls, and the walls meet at the manufacturer’s joint, the seam that was glued at the converter.
The printed face is not on that path. A heavier ink, a soft-touch film, or a foil stamp does not make the base carry more weight. If you change the board, the caliper, or the flap drawing, you have to redraw the path. Leaving the artwork and hoping the old glue-up still stands is how a carton fails in the mail without anyone changing the “design”.
This is also not a corrugated mailer. A folding carton organises and protects a surface. Do not specify it as if it were a shipping case.
How to check it
- Label the joint and the underside flaps on the drawing you are willing to stand next to.
- Trace the load from the product to the joint. If the trace only crosses the front panel, the spec is incomplete.
- When the board changes, reopen the path. Do not keep the old dieline by habit.
Usage
.carton-net .joint {
/* The seam is structural. Mark it as structure, not as trim. */
outline: 1px solid var(--accent);
}