Heise method

The first square was an outer square. We will pick a parallel inner square for the second square, since it can fit perfectly beside the first square. As before, the challenge is to build this square without destroying the first square.

In the example below, the existing (first) square is shown in white, and the second square that we would like to build involves the red/green pieces:

Notice that in the correct solution, the first square (shown in white) is moved out of the way before constructing the inner square.

Once both squares are constructed, they should be joined together so that they do not get in the way of other steps to follow: