Unused connections on Arduino board

Since I couldn't find any info about this through a forums search alone, I'll ask it here: what is the purpose of these undocumented through-holes?

Since they're most easily seen from the back, here's what I'm referring to:

I'm not, however, referring to the 4 connections labeled "X3".

Any ideas? I don't have software installed currently to view the board files, so I'm not sure exactly what they do.

They aren't unused if you have a voltage regulator. They are vias to provide the regulator with ground connectivity and a heat transfer path from the top ground plane to the bottom ground plane (probably more for the latter, since there are so many).

-j

As stated above, these are thermal transfer vias.

This allows the copper on the bottom to act as a heatsink for the voltage regulator on top.

This is a fairly standard method in PCB design. (Actually we usually use a grid of vias, as the holes get soldered in the wave machine, which helps it work like a heatsink)

Ah, that makes sense. I mean, I've heard of thermal vias, but never actually seen them in use.