trap door
Nipper at door

Nippers or Doortenders were the youngest of the underground workers, usually age 11 to 13. The job was an important one, since nippers controlled the heavy wooden doors that were part of the mine's ventilation system -- when the doors were closed, fresh air was directed into the chambers where the miners worked. Because nippers generally sat in the dark, listening for the rumble of approaching coal cars, they were often bored. But that did not mean the job wasn't dangerous -- if nippers fell asleep, they risked being killed in a crash. And if they were careless, or just fooling around, they often paid the price for the rest of their life.