1. Use a sheet of square paper. Crease the paper diagonally.
    Unfold. Then fold the paper in half.
2. Valley-fold the model in half again.
3.Turn the model over.
4. Valley-fold the top and bottom flaps.
5. Mountain-fold the model in half.
6. This is an enlarged model. Squash-fold the top right triangular
    flap.
7. Petal-fold the squash fold.
8. Valley-fold the petal fold to close it.
9. Squash-fold and petal-fold the second and third triangular flaps
    as in steps 6 and 7.
10.Squash-fold the left triangular flap.
11.Petal-fold the sqaush fold.
12.Valley-fold the petal fold.
13.Valley-fold the closed petal fold.
14.Crimp all the neck and head parts to bring them into slantling
     positions.
15.Inside reverse-fold the head parts to form the heads.
16.Valley-fold the wing to bring it upwards. Repeat behind.
17.Inside reverse-fold the tail to bring upwards.
18.The completed three-headed crane.