Catholics mark themselves with the sign of the cross as an outward expression of faith. The Catholic Cross is formed by two crossing perpendicular lines. The sign of the Cross over the body or the forehead, is made to resemble the Catholic Cross. According to the Catholic Encyclopedia, Catholics use the sign of the Cross in worship, sacraments and in prayer as a devotion to God and belief in the Holy Trinity, one God with three parts.
Join the thumb, index and middle fingers on the right hand. Joining these three fingers represents the Catholic belief in the Holy Trinity; Father, Son and Holy Spirit.
Fold the ring and pinky fingers into the palm. These fingers represent the Catholic belief that Christ is both God and man.
Touch fingertips to the forehead. Say "In the name of the Father." This phrase professes the Catholic belief in God, or Father.
Touch fingertips to the chest. Say "Son." This phrase professes the Catholic belief in Jesus, or the Son.
Touch fingertips to the right then to the left shoulder. Say "and the Holy Spirit." This phrase professes the Catholic belief in the Holy Spirit.
Place thumb on the forehead.
Trace a line down the forehead from top to bottom.
Trace a line on the forehead from right to left.
The sign of the Cross is also used by Episcopalians, Lutherans, Methodists and Presbyterians. The sign of the Cross made on the forehead can also be made on the lips, heart and additional body parts that need particular blessing.