Physics behind this bottle holder?

[ahhppull]

Homework Statement

What is the physics behind a balanced wine bottle holder. Something like this...http://www.thetipsygrape.com/product-racks-bottle-holders-straight-wood-bottle-balance.html

Homework Equations

No equations.

The Attempt at a Solution

I didn't know where to ask this question but I'm guessing this has to do something with the center of gravity and the angle that the wood was cut.

 

[inutard]

I would guess that the wood is angled so that any ~ 750mL bottle stuck in there would cause the centre of mass to fall right thru the base of the wood, thus allowing the contraption to balance.