A girl wearing a blank sandwich board.
sandwich board definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a pair of signboards hung, one in front and one behind, from the shoulders of a person paid to walk the streets displaying them
sandwich board definition by American Heritage Dictionary
Two large boards bearing placards, hinged at the top by straps for hanging over the shoulders with one board in front and the other behind, used for picketing or advertising.