An exit sign
An exit sign directed individuals to the nearest exit.
In 1986, there was an exit sign for sell at the Feinberg's Loan and Pawn antique shop. (Star Trek IV: The Voyage Home)
That same year, an exit sign hung over a door inside Mercy Hospital. (Star Trek IV: The Voyage Home)
In 2285, at Starfleet Academy, there was an exit sign marking the exit to the Kobayashi Maru simulation room. (Star Trek II: The Wrath of Khan)
On a holoprogram, there was an exit sign located backstage at Ronald B. Moore's comedy club. In 2365, Data and Guinan ran this program. (TNG: "The Outrageous Okona")