down to a gnat's eyebrow

down to a gnat's eyebrow

In consideration of the most minute detail. I have planned this itinerary down to a gnat's eyebrow, so we are not deviating from it, even for a minute!
See also: down, eyebrow
References in periodicals archive ?
As a result, American direct marketers can test down to a gnat's eyebrow and cash in big time on the rollouts.