is usually corner to corner 
. This
is represented by a dash-dot-dash line. Arrows will indicate which way the
fold should go.8. Main folds
Mountain fold: Means
fold behind along the line. This fold is usually corner to corner . This
is represented by a dash-dot-dash line. Arrows will indicate which way the
fold should go.
Valley fold: Means fold in front along the line. This fold 
is usually corner to side 
. It is represented by a dashed line. Follow the arrow on the picture to
know which way to fold.
Squash fold: in
a squash fold, some paper is opened out 
, and then flattened 
. A large thick arrow usually shows you where to press down.
Outside reverse fold: is
where a tip is folded inwards so that ends of the paper lie in between different layers
, so that two or more layers are folded along a single crease.
Inside reverse fold: is
where a tip is folded outwards so that ends of the paper lie in between different layers 
,
so that two or more layers are folded along a single crease.
Crimp fold: to make a crimp fold you
just have to make one valley and one mountain fold 
. An arrow looks like a lightning 
. A common
method of shaping a bird's head, a beak.
The Double Rabbit ear fold: This fold
is a bit like bending a drinking straw in half
.
It is used to narrow a triangular flap to produce a much thinner flap. It is a good way to
create thin legs on an animal.
Kite fold: This fold appears when you fold two flaps (corners) of
the paper to the central line 
.
Sink fold: this fold is
made when the center of the paper is folded inside the rest of the project
.