Spouseinbox and I were driving in Big City, Tx for a doctor’s appointment recently.  Spouseinbox noted the graffiti and mused what they were doing with such actions.  I stated the first thing which popped out of my dendrites.  It was my understanding that graffiti was the mark of a gang and as such they were showing their territory.  It is like the male cats traveling around their area marking their turf.  I guess it could be called visual cat pee.