How to make a long origami stairs

(page 20)

37th picture of long origami stairs

37.

Let's concentrate on the region encircled with a dotted circle of the step #36.

Prepare to apply a "valley-fold"

38th picture of long origami stairs

38.

Apply the "valley-fold" of the step #37.

Prepare to concentrate on the region encircled with a dotted circle.