ˈsandwich board noun [countable] two boards with advertisements on them that hang in front of and behind someone who is paid to walk around in public
[TahlilGaran] Dictionary of Contemporary English ▲
sandwich board n. Two advertising signs worn by a man, one on his chest and the other on his back.
The man walking along Main Street wore a sandwich board saying "Eat at Joe's." [TahlilGaran] English Idioms Dictionary ▲