Blessing oneself with two fingers brought to the thumb represents the Trinity. The last two fingers held to the palm represent the two natures of Jesus - God and man. For the first 1,200 years of the Church, in making the Sign of the Cross, the hand was typically brought from the right to the left shoulder. In the East this is still the practice, to signify Christ enthroned at the right hand of the Father. According to tradition and in the words of Pope Innocent III (1198-1216), the Sign of the Cross is made with three fingers because it is impressed upon us in the name of the Holy Trinity. From the forehead we pass to the breast, then from the right to the left. (Quoted in Gasparri: Catholic Catechism, p. 248).