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Phrase(s): know as much about something as a hog knows about Sunday
Rur. to have no knowledge of something. • Don’t let Jim make dessert for the picnic. He knows as much about pies as a hog knows about Sunday. • I had quite a time changing the tire, since I know as much about cars as a hog knows about Sunday.
McGrawhill's American Idioms And Phrasal Verbs