Fold one of the four flaps
to the center line. Note that the sharp point of the fold is at the open bottom side!
Now, fold the second
flap to the center line.
Turn the model upside down.
And fold the other
two flaps in the same way as before to the center line.
Like this. Now,
undo the two folds we just made
Open up the model at the bottom side.
And lift the paper, and
move the flap from the bottom side up. The point at the bottom will in the end be at the upside of the model.
Using the folds made before,
we move the sides to the middle line.
Here, the fold is in progres.
An additional, horizontal, fold line is made, as you can see.
We are finished with the step at this side.
Note that there is a flap, pointing upwards, that we could move downwards. The picture here shows that we can do it. We won't do it for the crane, however.
Flap moved downward.
Move the flap up, and turn the model upside down.
We do the same as at the other side: we undo the two folds made in the beginning.
Open the model at the bottom,
and lift the flap to the top.
When we are done, we finished the bird base.
Now, we can start from here making several types of birds, but let us look at how to make the crane.
From bird base to crane.