How to cut hard styrofoam

This tutorial video will teach you how to cut hard styrofoam.
Extruded Styrofoam is available at most hardware stores or home building depots. It is different than regular "bead" styrofoam-- it is not composed of pinhead-sized spheres. It is very workable. I call it "hard styro" since it is very durable. Yeah, it's kind of funny that I'm waving that knife around! The cameraman is actually about eight feet back. I guess the craft knife feels like a natural extension of my hand right about now.