Undershirts are often used for extra warmth under other clothing in cold weather. He added an undershirt beneath his sweater for the chilly evening.
Pro Tip 2/3
Absorbing Sweat
Wear an undershirt to absorb sweat and protect outer layers from stains. During the summer, an undershirt helps keep his suits fresh.
Pro Tip 3/3
Invisible Layer
Undershirts should not be visible around the neck or cuffs when worn under other clothes. He made sure his undershirt was tucked in and hidden from view.