We don't label sandwiches by what's on the outside.
If we did they would all pretty much be 'bread sandwiches'.
We name them for what's on the inside.
Be it ham, chicken, salad... You name it.
But sometimes we might mistake a tuna sandwich for a chicken one.
That's when you gotta realise you made a mistake or you're eating chicken tonight.
((I'm sorry this idea has just been in my head today and it took every amount of energy not to work 'knuckle sandwich' into the last line. "Quality" poem up next!))