"Storyteller" Giant's Head/Jaw Mechanism?

[shtick]

Anyone know of any diagrams or explanations on how the Giant's moving jaw is achieved? Its not animatronic. I know it was mentioned on the Jim Henson Hour Secrets of the Muppets episode.

http://images1.wikia.nocookie.net/muppet/images/1/18/Theheartlessgiant.jpg

I'm trying to build a mask/puppet head that has the same function.