know which end is up
not know which end is up
To be especially naïve, dimwitted, or uninformed. Give her a break—I didn't know which end was up when I was her age either. Local officials don't know which end is up when it comes to dealing with the housing crisis.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
know which end is up
tv. to be alert and knowledgeable. Don’t try to hustle me, sister. I know which end is up.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.