I've recently seen two great tutorials that disassemble the Kindle 3 for repairing. One is this great Fix your broken Kindle Keyboard Screen tutorial by ghwhitcher, and the other is the Amazon Kindle 3 Take-apart Guide by Powerbook Medic.
Both warn that on the display's back there is an extremely fragile layer of glass. ghwhitcher says that it is only kept unbroken for normal operation because the kindle3's case is strong enough to protect it to some degree. He actually broke it first, even with being careful I suppose, when disassembling—he warns.
My question is, what does this glass do? I mean, why does it screw the entire display part if it gets broken? What is this glass' function as part of the screen module?
illustration taken from the tutorial: