The text seems to be referring to 'trapping', in which each colour area is prtinted slightly larger than the space in the other colour; this makes the colours overlap slightly, which is less visible than having a white space if the colours happen to be slightly mis-aligned.

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E.g. for quality offset printing it is generally accepted that the trapping width should be between 1 and 1/2 print dots. When printing at 150 lpi the traps ...
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