Folding a valley-fold
Fold the lower edge upward to get your valley-fold. When you swing the lower edge down again, you will see a thin line indicating where the paper has been creased.
Folding a mountain-fold
Swing the lower part of the paper underneath the upper part of the paper to get a mountain-fold. When you swing the lower edge back again, you will see a thin line indicating where the paper has been creased.
The reverse-fold combines the valley-fold and the mountain-folds. In a reverse-fold, two or more layers of paper are folded together symmetrically along a single crease.
The reverse-fold comes in two types:
Inside reverse-fold (the most used)
Click here for the reverse-folds.