" You take your flashlight out on your walks, right?” Simon asked.
“Depends on the moonlight.”
“From now on, take it with you every night. When you’re out
walking this way, you’ll pass the gazebo, where, chances are, I will
be smoking.”
“Then what?”
“You can signal—say, three times if you want to take a walk with
me. Twice if you want to walk alone. that way I’ll just let you walk
on. It’ll be like a military code. No one gets hurt.”
I laughed. “that’s silly and charming.”
“I try. I can signal back with my cigarette lighter too,” Simon
said, holding up the lighter and firing off three short bursts of
flame. “So, like, if I see you first and I happen to not wish to talk to
you, I can fire off two bursts and block you in your tracks. "

― Amanda Howells , The Summer of Skinny Dipping (Summer, #1)