Know what this is?

If you are lucky, you don't have any idea. I found this on Rizal Street, right behind the Whole Foods, near my place. This is a piece of spark plug tied with a string. This is what the professional smash and grab thieves that patrol my neighborhood use to smash the windows of cars as they ride by on their bicycles. After the car alarm dies, they return to steal the contents. Needless to say, I found this one in a pile of shattered saftey glass. The car had been parked behind my mobile campaign headquarters, i.e. my 1973 VW bus. I've found spark plugs on the inside of my own vehicle after discovering a smashed window.