What's this bolt for?

No, really, I want to know. There is a short M3 bolt (that is the right name for the bolts that are all over the Makerbot, right) sitting at the bottom of my build area and... I have no idea where it came from. Everything I can see is still screwed in. Anyone know where this might have come from?

Sorry for the potato quality image. I'm concerned my bot is falling apart.