Wiktionary
know shit from shinola
vb. (context US English) To have the most basic level of intelligence or common sense.
Usage examples of "know shit from shinola".
I realized that I'd be spending the rest of my life treating smug, small-town hicks who didn't know shit from Shinola.
You see, Dick, I'm a cop, and I know what all cops know: that kidnappers are brainless scum who don't know shit from Shinola.
It's got me locked up in a hospital room in Georgia with a buttermouth little pissant doctor who doesn't know shit from Shinola.