Brainteaser II

Please excuse my crude Gimp illustrations.

Draw a line on your finger and a line on the rubber band with a pen. Carefully allign the line on the rubber band with the one on you finger so that the rubber band line lies directly above the line you drew on your finger.Ok, now take a rubber band and put both index fingers through it and pull them apart so that the rubber band is tight around them. Kind of like the tracks on a tank, but with only two wheels. Hard to explain, so here is a picture:

Now start twirling one finger around the other. Hard to explain so here is a really simplified frontal view of what you have to do:

I didn’t draw the line in my animation. That’s the brain teaser part. Does the line go back and forth from finger to finger, or does it go all the way around them both?

At first, you would immediately think it would go all the way around, but look closely…