I've discovered that a golf
ball banging into a piece
of metal 24 hours a day 7 days a week tends to take a toll on the
material in question.
You don't want to use anything
too heavy because it needs to vibrate somewhat when banged on. I'm
having some good luck with this lumber bracket shown in the video above.
It's a good thickness and
size that allows for easy mounting. A crescent moon shape helps catch
the golf ball while at the same time pushing it over the wall for
another revolution.