This is my first Instructable, so don't be too mean... and I am currently camera-less.
I am aware that it doesn't look that good, so lets say I'm posting just for the idea
Step 1: Ingredients
2 whole Altoids tins
4 fresh screws
Popsicle sticks (untested) or thin Ply-board (works)
1 clasp (optional)
4 more screws (if you want a clasp)
Anything you can use as an anvil that fits in your Altoids tin sideways with your desk
Something to cut the wood with
Rotary tool to banish the screwtips on the inside of your tin
Step 2: Decapitate the Twin Tins
Step 3: Flatten the Hinge-ish Things
Step 4: Doing Hinge Stuff
Before making the holes you want to have something on the other side, which is where the ply-board or Popsicle sticks (I'm not sure if the Popsicle sticks work) come into play. You want to cut a piece about the width of a Popsicle stick and the length of your clasp, and set this behind where your clasp is going to go. Grasp your hammer and, with a thin nail, puncture a hole (in the middle of your hinges hole) in the Altoids tin and partway through the wood. Remove the nail and screw the screw into place. Do this to the other side of the hinge.
Now comes the other half. You want to make sure the edges of the tins will meet cleanly, so hold the two half's together together and mark little dots where the screws go. I thik the rest is fairly self-explanatory; just screw on the other half.
Step 5: Rid Your Insides of Screws
Step 6: Optional Steps
It is also possible to add a clasp to the tin, using the same method you used for the hinge.
Step 7: Finished!!!