can't make heads or tails of
can't make heads or tails (out) of (someone or something)
Cannot understand someone or something at all; cannot make any sense of someone or something. I've been working with the new software for hours, but I still can't make heads or tails out of it. I can't make heads or tails of that new guy in accounting. Sometimes, he's really friendly, and then other times he acts like he's never met me before.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
can't make heads or tails (out) of someone or something
Fig. [to be] unable to understand someone or something. (Also with cannot.) John is so strange. I can't make heads or tails of him. Do this report again. I can't make heads or tails out of it.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.