Die a Hero
Judging by the black and white graininess of this picture, we can only assume that this picture was taken sometime in the mid-20th century. The purpose of the contraption shown here is to lock the hand of someone who pulls a fire alarm. People were probably sick and tired of evacuating entire buildings for pranksters raising false alarms.
So, the solution was to lock the hand of the person, just in case they were indeed pulling a prank. If they weren’t, they would’ve been swallowed up by the fire. The good news is that they would’ve burned to a crisp as a hero.