How to make a simple origami space shuttle

(page 10)

17th picture of simple origami space shuttle

17.

Apply the horizontal valley-fold of the step #16.

Do the same for the other side also.

Prepare to apply a horizontal valley-fold.

18th picture of simple origami space shuttle

18.

Apply the horizontal valley-fold of the step #17.

Prepare to unfold the horizontal valley-fold that you have just applied.