Kneeling and praying with beads, crosses depicting a crucified Jesus, and sprinkling holy water on this and that are telltale Catholic practices. The meaning behind them relates to the body and soul — the dynamic between the material and spiritual worlds.
The sign of the cross
The most common Catholic gesture is the sign of the cross. Latin (Western) Catholics make the sign of the cross by using their right hand to touch the forehead, then the middle of the breast, then the left shoulder, and finally the right shoulder. As they do this, they say, "In the name of the Father and of the Son and of the Holy Spirit, Amen." This one complete gesture makes a cross — an intersection of a vertical line from forehead to breast and a horizontal line from left to right shoulder.
Byzantine Catholics make a similar sign of the cross but go to the right shoulder first and then to the left. Byzantine Catholics are former Eastern Orthodox Christians who split from Rome in 1054 and who came back into full communion in the 17th century by accepting the authority of the bishop of Rome as pope and head of the Church. They include the Ruthenian, Ukrainian, Greek Catholic, Melkite, Romanian, and Italo-Albanian Byzantine Churches. In addition to the Byzantine, Eastern Catholics also include Maronite, Coptic or Chaldean Catholic Churches, which are in union with Rome as well.
Most importantly, the sign of the cross symbolically reaffirms for Catholics two essential Christian doctrines: The Holy Trinity — Father, Son, and Holy Spirit — and humankind's salvation through the cross of Christ.
The genuflection
Another telltale sign of a Catholic is genuflection, which is touching the right knee to the floor while bending the left knee. The sign of the cross is made simultaneously with this gesture. Catholics only genuflect in front of the Holy Eucharist. The Holy Eucharist is the real body and blood of Jesus, so Catholics show the ultimate form of respect by genuflecting or kneeling before him. The Holy Eucharist is kept in a large metal container or vault called a tabernacle, or sometimes, the Eucharist is displayed behind glass in a gold container called a monstrance.
The crucifix
The crucifix is a typically Catholic symbol, a cross bearing an image of Jesus being crucified. Protestant Christians typically have crosses with no corpus (that's Latin for body) of Jesus attached. The graphic symbol of the crucifix became predominant in the Western Church to remind Catholics that Jesus was true man as well as true God and that his suffering and death were very real and painful. The crucifix reminds Catholics of the high price paid for humankind's sins and inspires believers to repent of their sins and be grateful for the salvation obtained by Jesus' death on the cross.
Holy water
Holy water is a sacramental — a religious object or action created by the Catholic Church as opposed to those instituted by Jesus himself. Helpful and beneficial but totally optional, sacramentals are inferior and subordinate to the seven sacraments, which are necessary in order to live a life made holy by the gift of grace from God. Sacraments give the recipient a special grace necessary to fulfill the mission of that particular sacrament, but sacramentals offer a different and subordinate grace depending on the spiritual demeanor of the recipient.
Sacraments are like food for the soul, and sacramentals are like supplemental vitamins.
Holy water, which is water blessed by a priest, bishop, or deacon, is the most widely used sacramental. Non-Catholics may think of holy water as the stuff that burned the face of the possessed 12-year-old in the movie The Exorcist. Holy water can be used to drive out demons; so on rare occasions the Church uses it for that purpose. But more regularly, holy water is used as a symbolic reminder of Baptism. On entering or leaving a church, Catholics dip their right hand, usually with two fingers, into a font, a cup of holy water that's on a wall near the doors of the church. Then they make the sign of the cross, wetting their forehead, breast, and shoulders. They're visibly reminding themselves that they're entering the House of God, the Holy of Holies, and blessing with holy water is good preparation for worship.
Anytime a priest or deacon blesses a religious article, such as rosary beads, a statue, or a medal of one of the saints, he sprinkles holy water on the object after saying the prayers of blessing. The holy water reminds the owner that the object is now reserved for sacred use — to enhance prayer life, for example, and shouldn't be used for profane (nonreligious) use. Likewise, a blessed cup, called a chalice, used at Mass to hold the wine that the priest consecrates, can't be used for any other purpose. It can't be used to drink wine or juice at the dinner table, for example.