A phrase heard at, and a sign sometimes seen at, golf courses. What this is saying, is when you happen to make a divot, please have the good nature and responsibility to pick up the turf and put it back where you so savagely ripped it from.
It's not as hard as it sounds. Because lumps of grass are seldom aerodynamic, they won't travel far. Just pick it up, and put it back the way it was. This means lining it up the right way in the wound, pushing it flush with the rest of the grass and, if you're really nice, tucking the edges down as to make it harder to see. Someone I know even goes so far as to put a sprinkle of fertilizer down on the dirt before he replaces them to encourage regrowth, but no one (in their right mind) will mandate that.