not be able to tell one end (of something) from the other
To have absolutely no knowledge about something. I'm not able to tell one end from another when it comes to computers, so you'll have to explain this to him really slowly. Jeff wouldn't be able to tell one end of a baby from another. Thank goodness Frank is there to help babysit.
not know one end (of something) from another
To have absolutely no knowledge about something. I don't know one end from another when it comes to computers, so you'll have to explain this to me really slowly. What's an attachment again? Jeff wouldn't know one end of a baby from another. Thank goodness Frank is there to help babysit.