Whereas, the Star of David can be divided exactly in to two, the two halves being triangles, one pointing upwards (towards Heaven) and the other pointing downwards (towards earth). To the Jews, these two triangles represent Heaven and Earth.
To Take it a little further, to us Christians, the downwards pointing triangle, each of the top points represent God and Jesus, the base point The Holy Spirit, all pointing towards man. The upwards pointing triangle, at the base points are man and woman, the apex point being Jesus, All pointing towards God the Father.
As the two triangles are perfect, and the two together equals 360 degrees, (a circle - representing the never ending love of God), if the two triangles are put together in such a way as to form a square, we then have our 'Four Square Gospel!!'