not able to make head nor tail (out) of (something)
Failing or unable to understand, decipher, or make sense (of something) in the slightest. We tried identifying the heiroglyphs on the ancient tablet, but they were so archaic that we weren't able to make head nor tail of it. See if you can figure out what this contract is saying—I wasn't able to make head nor tail out of all that legal mumbo jumbo.