The name of this base speaks for itself. You can see the head, tail and two fins. It is necessary only to form their.

On the first diagram we precrease the diagonal of the square, as well as at folding of the triangle. At the following two stages precrease the two kites from the opposite directions.

In the fourth diagram we continue to percrease. We shall mark the parts of the second diagonal. And, at last, at the fifth stage by one movement we shall give to the model its final form. This most difficult action.

On this base form are based the following classical models: the carp and the seal.