What Catholics Believe - The Sign of the Cross

Why Do Catholics Make the Sign of the Cross?

First off, when we make the Sign of the Cross we also say, outloud or silently, "In the Name of the Father, the Son and the Holy Ghost."  It is a statement of our Faith, our creed, our belief in the One God in Blessed Trinity.  Note, we don't say "In the names ..." but "In the Name of...", why?  Because it is a small testimony of the Doctrine of the Trinity, while Three Divine Person - there is only One God.

The Catechism of the Catholic Church (hereafter "CCC") tells us:

232 Christians are baptized "in the name of the Father and of the Son and of the Holy Spirit"⁵³ Before receiving the sacrament, they respond to a three-part question when asked to confess the Father, the Son and the Spirit: "I do." "The faith of all Christians rests on the Trinity."⁵⁴
233 Christians are baptized in the name of the Father and of the Son and of the Holy Spirit: not in their names,⁵⁵ for there is only one God, the almighty Father, his only Son and the Holy Spirit: the Most Holy Trinity.

Footnotes:
53 Mt 28:19.
54 St. Caesarius of Arles, Sermo 9, Exp. symb.:CCL 103,47.
55 Cf. Profession of faith of Pope Vigilius I (552):DS 415.

The Sign of the Cross is a Sacramental

So, what is a sacramental?  Again, going back to the CCC:

1667 "Holy Mother Church has, moreover, instituted sacramentals. These are sacred signs which bear a resemblance to the sacraments. They signify effects, particularly of a spiritual nature, which are obtained through the intercession of the Church. By them men are disposed to receive the chief effect of the sacraments, and various occasions in life are rendered holy."¹⁷³
The characteristics of sacramentals
1668 Sacramentals are instituted for the sanctification of certain ministries of the Church, certain states of life, a great variety of circumstances in Christian life, and the use of many things helpful to man. In accordance with bishops' pastoral decisions, they can also respond to the needs, culture, and special history of the Christian people of a particular region or time. They always include a prayer, often accompanied by a specific sign, such as the laying on of hands, the sign of the cross, or the sprinkling of holy water (which recalls Baptism).
1669 Sacramentals derive from the baptismal priesthood: every baptized person is called to be a "blessing," and to bless.¹⁷⁴ Hence lay people may preside at certain blessings; the more a blessing concerns ecclesial and sacramental life, the more is its administration reserved to the ordained ministry (bishops, priests, or deacons).¹⁷⁵
1670 Sacramentals do not confer the grace of the Holy Spirit in the way that the sacraments do, but by the Church's prayer, they prepare us to receive grace and dispose us to cooperate with it. "For well-disposed members of the faithful, the liturgy of the sacraments and sacramentals sanctifies almost every event of their lives with the divine grace which flows from the Paschal mystery of the Passion, Death, and Resurrection of Christ. From this source all sacraments and sacramentals draw their power. There is scarcely any proper use of material things which cannot be thus directed toward the sanctification of men and the praise of God."¹⁷⁶

Footnotes:
173 SC 60; Cf. CIC, can. 1166; CCEO, can. 867.
174 Cf. Gen 12:2; Lk 6:28; Rom 12:14; 1 Pet 3:9.
175 Cf. SC 79; CIC, can. 1168; De Ben 16,18.
176 SC 61.
177 Eph 1:3.
178 Cf. Mk 1:25-26; 3:15; 6:7, 13; 16:17.

So, sacramentals are things we do which enrich our Faith, which bring us closer to Jesus Christ and serve as reminders of our Creed and the Sacraments.  This is precisely where the Sign of the Cross fits in - it is a testimony to the Trinity and it brings remembrance of our Lord's suffering on the Cross which is also reflected in the Sacrament of the Eucharist.  The Sign of the Cross often is made to "bless one's self" but it is also used to bless others - such as when the priest does so at the end of the Mass - all those in attendance, even non-Catholics, receive a blessing - a small amount of grace.  Anyone who is doing what the Church intends can perform the sacramental of the Sign of the Cross.  While the almost automatic, Sign of the Cross is quite simple, it has meaning which is quite profound.

How do we make the Sign of the Cross?

Start by holding your fingers of your right hand like this:

 
In the Latin Rite:

The Eastern Rites are virtually the same, except that they go to the right shoulder first, then the left: