Hinge Help!

I'm having a hard time finding a particular hinge I want to use on a project.
This hinge is similar to an offset hinge, but not close enough for me to use. Here's a ASCII sketch of what I'm talking about: Bd 1 Bd 2 Bd 3 ||.......|........||......| ||_______|_______.||______|
.^.......^.......^........^ .1.......2.......3........4
1: Shows the hinge on the outside of Board 1 2: Shows where Boards 1 and 2 abut 3: Shows where the pivot point is 4: Shows the board that I want to pivot
Basically, I want a hinge that will screw into Board 1, go over the end, pass over Board two entirely, and screw into Board 3. The plan is to have Board 3 pivot up so Board 2 can slide under it, and support Board 3 when it's at full extension. So the hinge itself would look like this: |............| |___________.|
Has anyone seen a hinge like this? I've done a bit of searching through Google, but mylack of knowledge in hinge terminology puts me at a disadvantage.
PS: My crummy ASCII "art" will probably look funny outside of the Courier New font. I'm using Google Grounps, so I'm not sure how it will look on your viewer. Hopefully you'll be able to understand WTF I'm talking about!
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