It's amazing to surround yourself with papercrafting friends who like to share ideas- my coworker was trying to explain a new fold to me, and I was having a heck of a time trying to get what she was saying... I am more of a visual person, and do better with hands-on than someone explaining something to me. So, after work, I went to one of my favourite sites- Splitcoast Stampers- to find the instructions for the tri-fold shutter card. It's a really pretty card, and does take some time and calculation (not my strength, but fortunately my husband comes to my math rescue!).
As this was only an experiment, I grabbed what was close at hand, and didn't really have much rhyme or reason for the materials I used.
The only change I would make to the directions of the card is to make the 1 3/8 by 1 3/8 card pieces a little larger so they fill up a little more of the space.