Tools & supplies for this project:
1) DUCT TAPE
2) cardboard (two, 10X10 inch squares)
3) two plastic shopping bags
4) one 30 inch shoelace
Step 1: Layout
Set your two cardboard squares about 1.5 to 2 inches apart on a surface that won't be damaged by the duct tape. I used a 'self-healing' cutting board laid out on the family washing machine. (It was raining and I didn't feel like running out to the garage to do this.)
Step 2: Taping
Cover the cardboard with duct tape (neatness counts).
Oh - before you start taping - lay the shoestring down the middle of the two pieces of cardboard. Tape over it. If you do this part right, you'll have about 9 inches of lace hanging off of each end. You'll need this to tie the case shut, later.
Color outside the lines: the duct tape should overhang the cardboard by about an inch all around.
Step 3: Flip the case
Flip the case over.
It should now be sticky side up on your work surface.
Notice that I didn't follow my own advice about an inch overhang all'round. (*sigh*)..
Fold the overhanging tape over the raw cardboard edges. Add tape as necessary if you didn't leave enough overhang.
Cover the gap of sticky tape between your cardboard cavers with more duct tape and tape the edges of the covers down to make sure they don't come undone.
Your map case should look something like a binder by now...