How to make a simple square origami spring

(page 10)

17th picture of simple square origami spring

17.

Start applying four "open sink-folds" of the step #15.

Let us concentrate on top and bottom ones (indicated as #1 and #2).

Prepare to finish applying two "open sink-folds" there.

18th picture of simple square origami spring

18.

Complete applying two "open sink-folds" of the step #15.

Now, we need to make sure if we are applying both two "valley-folds" and two "mountain-folds" for top and bottom sides according to the step #14.

Prepare to rotate the model by 90 degrees.