I picked this up in a store in Tokyo last year. We had no idea what it meant until I asked the lady at the counter, who told us it was a sign for a fire extinguisher. I thought it looked cool and bought it anyway, in a moment of tourist stupidity.
When we got home we were surprised to find we had a fire extinguisher tucked away under our kitchen sink. So now the sign points it out, though few of our guests will understand it.