not be able to tell one end (of something) from the other

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.
See also: able, end, not, one, other, tell

not know/not be able to tell ˌone end of something from the ˈother

(informal) know absolutely nothing about something, for example a machine: Don’t ask me to fix the car. I don’t know one end of an engine from the other.
See also: able, end, know, not, of, one, other, something, tell