know which end is up

From the common marking this end up on parcels to guide proper transport.

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know which end is up (third-person singular simple present knows which end is up, present participle knowing which end is up, simple past knew which end is up, past participle known which end is up)

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

   Synonym: know which way is up

   He was too stoned to know which end was up.

   • 1992, Dorothy Garlock, Glorious Dawn‎, →ISBN:

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

   • 2005, John C. Hefley, Failure Equals Death, →ISBN, page 29:

     “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.”

   • 2009, Lis Wiehl, April Henry, Face of Betrayal, →ISBN, page 145:

     “I'm not some naïve, virginal little nothing who doesn't know which end is up.”

   • 2010, Gordon Lish, “The Friend”, in Collected Fictions, →ISBN, page 243:

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

   • 2011, Richard North Patterson, Silent Witness, →ISBN, page 277:

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

   • 2011, Catherine McGuinness, Emperors' Clothes‎, →ISBN, →ISBN:

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

Frequently used in negative constructions to discuss inexperience or failing to understand a situation. Cf. know one's ass from a hole in the ground.

• know one's way around
• know which side one's bread is buttered on