About 9 years old, found a really nice jackknife when I was out fishing.
My neighbor honed it to a razors edge for me. I then proceeded to slice my right hand wide open from wrist to that flesh between thumb and forefinger. He bandaged it up and my mother thought it was minor. A few days later, she removed the bandage and near freaked.
The scar has shrunk some over the years but it's still 3 inches long.
Never done that again