Rune rumination

George: I am not giving you my code.
Kramer: I'll bet I can guess it. Let's see... Well, we can throw out birthdays immediately. That's too obvious. And no numbers for you. You're a word man. Let's go deeper... What kind of man are you? Well, you're weak, spineless, a man of temptations. But what tempts you? You're a portly fellow. A bit long in the waistband. So what's your pleasure? Is it the salty snacks you crave? No no no no... Yours is a sweet tooth. Oh, you may stray, but you'll always return to your dark master... The cocoa bean! And only the purest syrup nectar can satisfy you. If you could, you'd guzzle it by the gallon... Ovaltine!? Hershey's!? Nestle's Quick!?"
- Seinfeld, The Secret Code

BCer Oli writes:

A woman called round a friend's house on Florence Road in a state of (seemingly) genuine distress, clutching a electricity top-up stick saying that she 'lived at number X' and that she was home alone with her three kids and no cash and her husband was out until later; that the electricity meter has unexpectedly run out, and would they mind awfully lending her a small amount of money that she would return as soon as her husband was home (I think you can see where this is going).

My friend, drawn in her by her remarkable acting skills (nor did she have any visible signs of addiction problems or homelessness that might have raised a suspicion of genuineness) invited her in, introduced her to his partner, and told her to sit down whilst he gave her ten pounds. Of course she didn't come back, and no one had ever heard of her at the address she claimed to live at.

But this is where it gets really weird... my friend called the police and they told him to check the outside of their house, and that there might be a symbol chalked on the wall. Sure enough there was a discrete rectangle daubed by the front door. Apparently it's one of a set of signs made for others in the gang, though the police don't know what each one means – anything from 'don't target this house again' to ' there's a nice big telly in here to come back later for'.

They didn't care about the ten pounds, but were understandably freaked by the signalling. Has anyone experienced something similar?