I can’t seem to write today so I’m going to break this down via pictures. Here are the fundamentals though. You should wear an undershirt. You should especially wear an undershirt when you’re wearing a button-up shirt in a thin enough fabric that a person can tell whether or not you are wearing an undershirt. An undershirt will also help to avoid taco pits in the summer. Lastly, don’t wear a crew-neck T-shirt as an undershirt if you’re wearing your caller open. It’s a mistake.
You want to follow the sartorial lead of the original Brawny man.
Not his safe and stylistically-challenged “upgrade.”