I'm experimenting with pull tab mechanisms for my Levers eBook. I need a tab that I can pull that will remain lined up with its direction of movement. It needs to move easily.
I've made a tube to run the pull tab inside. The first draft used a simple 'V' shaped fold to hold the tab (Top picture). If the moving tab is anything but completely straight it wedges into the corner of the fold and becomes hard to move. To overcome this I used a double fold as shown in the bottom picture. It only need to be half a millimeter across and suddenly the tab moves freely.
It adds depth to the page but works really well.