lock the barn door after the horse has bolted

Idioms and Phrases

Also, lock the stable door after the horse is stolen . Take precautions after damage has occurred. For example, After the burglary they installed an alarm system, but it's locking the barn door , or Deciding to negotiate now after they've been fired—that's a matter of locking the stable door after the horse is stolen . These expressions of action that is useless because it comes too late have long been proverbs in many languages and first appeared in English in the mid-1300s.