Y'know those plastic divider bars they have at supermarket checkout counters, to separate one person's groceries from the next? There's gotta be a store somewhere that sells those. Thing is, if you go there and buy some divider bars, how do you keep them separate from the next guy's divider bars? Do they use divider bars too? And if so, how do they keep track of it all? "No, I'm not buying that one, that one's *yours*!"