placard
A handheld sign used to show a message in public.
A placard is a sign, usually made of cardboard or poster board, that someone carries or displays to share a message with others. When you see news coverage of a protest or rally, many people hold placards with slogans, demands, or statements written on them. Workers on strike might carry placards explaining why they're protesting. At airports, drivers often hold placards with travelers' names so people can find their rides.
Placards work because they're portable and visible. A person can make one at home with markers and poster board, then carry it to wherever people will see it. They're different from permanent signs or billboards: placards are temporary, handmade, and personal. The word suggests something simple and direct, a way to make your voice heard in public.
You might also see placards in less serious situations. Sports fans create placards cheering for their teams. Students might make placards for a school election campaign. Anywhere people want to share a message with a crowd, placards turn up as a simple, effective tool for communication.