Step 19 :
Fold as show below.
Step 20 :
Turn over.
Step 21 :
Fold behind along the dotted line.
Step 22 :
Turn over along the arrow.
Step 23 :
Pull up the upper layer.
Step 24 :
Make creases along the dotted line.
Step 25 :
Fold the bottom edge up along the crease made in step 24.
Step 26 :
Flatten along the arrow.
Step 27 :
Pull down the upper layer.
