speak by the card

speak by the card

To speak with accuracy and exactness. The "card" in this now-obsolete phrase might have referred to a sea chart, which was considered very precise. I always trust a man who speaks by the card—it inspires great confidence.
See also: by, card, speak
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
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References in classic literature ?
At any rate, it was more like a hearse than any thing else, though to speak by the card, it was a gondola.
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