What Is That Hole In A Knife Blade Really For?

It's not uncommon for the blade of a knife to have holes in it, but why is that? What are they there for and does it help ...
Knives Project on MSN

Heat the screws, make the knife: A blade in the making

What happens when you try to make a razor-sharp knife from 350 razor blades? Or forge a battle-ready blade from old drill ...