I recently stumbled on this photo from 1992 or 1993. Look at how dark my hair was -- no gray at all!
That's a cinder block cap that I'm hitting, and you'll notice I'm hitting it with my left hand. And I am not left handed.
The reason is, I'd injured my right hand doing this break a few weeks earlier. If you know this stuff and see my bad body mechanics here, you won't be surprised to learn that I injured myself here too. (In both instances the caps broke, but I bruised my wrist bones.)
This photo from the archives (click on it for a larger version), from when I was a brown belt in 1992 or so, shows me about to break a cinder block cap during a intramural tournament. It's not a terribly impressive break -- I really need to be in a lower stance and drop my center of gravity more -- but you may notice that I'm performing the break with my left hand. And I am not left handed.