How to remove glass doors from a fireplace?

This is a little hearth related but I thought I should put it here. There are glass folding doors on my fireplace with a screen inside them. They look a little bit like this


We need to take them off to roll our monster insert in there and see how things fit. I can't see any visible screws or anything, but if I grab the whole frame at the top, I can rock the whole frame from the bottom outwards, so I know it's only really attached at the top. There's fiberglass insulation along the sides so perhaps that's hiding the attachments, but I can't quite figure it out.

Do you suppose if I slide it a little in one direction or another it might be in sort of slots that will unengage or something?

By George I think I've got it! I quit searching for "how to remove" and started looking for "how to install" - found a step by step right away that probably solves my problem.
http://www.thisoldhouse.com/toh/how-to/step/0,,1154375,00.html