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general::
Phrase(s): put something down in black and white [and] set something down in black and white
Fig. to write down the terms of an agreement; to draw up a written contract; to put the details of something down on paper. (Alludes to black ink and white paper.) • We agree on all the major points. Now, let’s set it down in black and white. • I think I understand what you are talking about, but we need to put down the details in black and white.
McGrawhill's American Idioms And Phrasal Verbs