I have read this story in several versions on different websites over the years. It’s a teaching story, a parable, a long Zen koan. This is my own recollection of the story filtered through different versions and through a somewhat faulty memory.
There was a young boy who unfortunately had a very bad temper. One day at the start of summer, his father gave him a hammer and a box of nails. He told his son that every time he lost his temper, he had to hammer a nail into the back of their fence.
Just on the first day, an angry day, the boy slammed two dozen nails into that fence.
But the number of nails decreased every day.
Maybe each nail was a solid reminder of his anger. Looking at the nail heads was a reminder of how many angry moments the boy had over the weeks. Maybe pounding nails was a way to release that anger. I think it was both of those things working together.
It worked. By the dog days of August, the boy didn’t lose his temper very much. He didn’t hammer any nails for three days in a row.
His father was proud of his son, but the lesson was not over.
The father told his son that it was now time to pull out one nail each day that he was able to hold his temper. Removing nails took the boy through the end of summer and into autumn.
It was just before Thanksgiving when the boy came to his father and said that all the nails were gone.
The two of them stood by the fence and his father said, “Look at all the holes in the fence. Even with the nails removed, the fence is forever changed. It will remain scarred. When you say or do things in anger, it leaves a scar. Even if you remove those nails, the wound remains in some form. Making up for things we have done that are wrong is good. Forgiveness is good. But some wounds don’t heal, and some people cannot forgive. Think before you drive a nail of anger.”