Quadrifolds, folding types
There exist several kinds of 4-panel folds...
In Roll Folds, the front and back cover panels are of the same size, but the two panels that fold inwards should be shorter. Specifically, the panel next to the back cover (which we will call "wrapping panel 2", should be 2 mm. narrower, and the outer panel (which we will call "wrapping panel 1"), should be 2 mm. shorter than the "wrapping panel 2", in other words, 4 mm. less than the front and back cover panels.
Double Parallel Fold
If the fold is double parallel, all four panels are the same size. This is consistent with the concept that this type of folding is actually a bifold + another bifold, and in a bifold panels are always equal in size (unless it is an asymmetric bi-fold).
In the case of an accordion fold all the panels have to be the same size. If a quadrifold's size is 10 x 21 cm, the 4 panels should measure 10 cm. When designing quadrifols folded into an accordion, it is necessary to bear in mind on which panel to place the cover and on which panel to place the back cover. Specifically, looking at the external side, the cover corresponds to the panel on the right, whereas the back cover is the panel on the left.