lock the barn door after the horse is stolen

lock the barn door after the horse is stolen

To try to prevent or rectify a problem after the damage has already been done. My father quit smoking after he was diagnosed with lung cancer, but I'm afraid he's locking the barn door after the horse is stolen.
See also: after, barn, door, horse, lock, stolen
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

lock the barn/stable door after the horse has bolted/is stolen, to

To take precautions after damage has been done. This proverb, found in many languages, first appeared in a French collection of ca. 1190 and found its way into a Middle English manuscript, Douce MS, by about 1350. It has been repeated ever since. Stanley Walker poked fun at it (The Uncanny Knacks of Mr. Doherty, 1941): “He locked the stable door while they were putting the cart before the horse.”
See also: after, barn, bolt, door, horse, lock, stable, to
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer