litter on a stick n. roadside billboards, signs, and advertisements. (source: Double-Tongued Dictionary)
Further reading
Professional dog walkers call a dog obsessed with carrying sticks a branch manager. Another dog who grabs the other end of the stick and helps carry it around is jokingly called an assistant branch manager. This is part of a complete episode.
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Smaller signs are referred to here (http://www.causs.org/) as street spam, vertical litter, bandit signs, snipe signs, utility pole advertising, stuff on a stick