know which end is up

• know which way is up

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know which end is up

1. (idiomatic) To possess sound judgment or common sense; to have a clear understanding of a situation.

   He was too stoned to know which end was up.

   • 1992, Dorothy Garlock, Glorious Dawn, →ISBN, (Google preview):

     He's so in love, he doesn't know which end is up.

   • 2005, John C. Hefley, Failure Equals Death, →ISBN, p. 29 (Google preview):

     “I'll gladly take criticism from a cop who knows which end is up and isn't afraid to do the job the way it should be done.”

   • 2010, Gordon Lish, "The Friend" in Collected Fictions, →ISBN, p. 243 (Google preview):

     “[B]elieve me, she is some catch for the right boy—for a boy which knows which end is up.”

   • 2011, Catherine McGuinness, Emperors' Clothes, →ISBN, 9781937110048, (Google preview):

     The whole company is in disarray! Nobody knows which end is up.

• Usually used in negative constructions, such as:

2011, Richard North Patterson, Silent Witness, →ISBN, p. 277 (Google preview):

“When someone doesn't know which end is up, who knows why they do things.”

• know one's way around
• not know which end is up