Pureland folding allows only simple valley and mountain folds. Since a pleat
can be folded by first making a valley and then a mountain,
that uses only a sequence of pleats, however complicated, belongs to
This gallery indicates some directions for pleat-based
folding that incorporates more complex steps.
The first two pieces here are based on layering multiple second-order
pleats to create loose paper.
The second two use twists in order to reverse parts of each pleat
and create new layer and tension patterns.
The first technique has been used by several other folders to create
boxes, crosses and other types of mostly regular protrusions.
It has also
been used for a long time in box-pleated models such as Momotani's Steam
Medium: elephant-hide; unryu.