a really dumb question

A story from the old days.........Early seventies, after I got out of the Navy, a friend calls me one day, he junked out some cars. Said he had a wheel and front hub drum he could NOT get apart, "could he come out and borrow my impact?"

"Sure"

Now this guy lived about 15 miles from me, so he comes out, drops the wheel/ hub on the ground, and I said, "Mopar, uh?"

"How'd ya know"

"I can tell by lookin' at the wheel. WHICH SIDE IS IT OFF OF?"

And this funny look starts across his face, LMAO