Files & prepress
What is knockout?
A knockout removes the background colour behind an overlying element, so the top colour prints on unprinted media rather than mixing with what's beneath it.
It's the default behaviour and usually invisible — yellow text on blue knocks a text-shaped hole in the blue so the yellow prints clean instead of turning green. The term earns attention at the boundaries, where knockout and overprint choices interact with registration.
In signage the word also gets used loosely for reversed-out designs — 'knock the logo out of the panel colour' — meaning the logo is unprinted substrate showing through a printed field. Same idea, larger scale.
Related terms
Software that speaks the trade
PrinterFlo runs print & sign shops on one board — quotes that price by size and material, proofs approved from one link, and a production checklist the quote writes for you.