TIL that finishing a shaped metal sheet by pounding it on a pedestal is called "planishing" and said pedestal is called a "planishing stake." I've seen it done I just never thought to ask what it was called, I guess.
I'm what the aerospace industry calls a "surface enhancement engineer." A fancy way of calling me a peener. I mostly work with CNC air blast shot peening machines but the principle is essentially the same as a ball peen hammer.
Basically, hitting metal with hard ball causes little dimples to form on the surface of your work piece. Hit it a shit load of times and you get dimples all over. At the end of the day all those dimples help prevent stress fractures from forming.
Fun hammer fact: it's called dead blow not because it's supremely powerful or anything, but because the head is usually full of loose material like BBs, and it causes the hammer to not bounce back as much, kinda like throwing a hackey sack at the floor