Part 2 Valley folds and Mountain folds.
These are the two simplest folds in origami. A valley fold means fold
in front along the line. This is represented by a dashed line.
A mountain fold means fold behind along the line. This is represented
by a dash-dot-dash line. Some books represent it as a dash-dot-dot-dash
Together, almost all folds in origami are combinations of these two
folds, in one way or another. Some models are composed entirely of one
mountain or valley fold at a time. These are called Pureland folds. These
models are often the simplest types of model to fold, although some of
them can be pretty complicated.
This is a simple model to start you off with. It is a simple
Samurai helmet, part of the armour worn by a Japanese warrior. It is
modelled here by a cuddly Tasmanian Devil. All the folds are valley
and mountain folds. A 12" square of paper produces a hat 8" wide,
which should be big enough for most heads.|
here for diagrams