"I'm thinking of something that keeps people out!" the Oldest hollered so all in the back could hear.
"a dog!" the Girl said.
"a closed door!" Eraser Eater said.
"a slammed door!" Eraser Eater said.
"a gun!" (we all laughed) Eraser Eater said.
"a sign!" I said.
"Yep!" the Oldest nodded, "it's a sign. You know, like 'keep out!', 'beware of dog.' I am surprised you didn't get it sooner. Why would it be a closed door?"
"Well, I mean, sometimes a sign doesn't keep people out," I said.
"What do you mean?"
"Well, you could have a wide open door with a sign on it that says 'keep out' but people would still come in because it was open."
"Oh great!" yelled the oldest with a laugh.
"I bet if a signed door were opened and a guy were sitting there with a gun they'd keep out!" Shouted Eraser Eater.
I laughed for about two minutes straight. I think he gets it from me.