This was designed to be cut from a 8.5x11 piece of cardstock, so if you resize it to be shorter or use a larger piece of cardstock, you'll need to add vertical lines on each end to connect the top to the bottom.
The reason why there are tabs on both ends (as you'll see when you open the file) is because I stapled them in addition to gluing together (on the inside, of course) for reinforcement.