Sacramental designates any object or action which the Christian church makes available to persons as an aid to salvation and increased spiritual growth toward God. It is intended as a sacred sign or representation of supernatural grace or blessing and also for protection of God from evil.
Sacramentals fundamentally differ from sacraments. While sacraments are said to actually confer the grace of God by the established ordinance of the Lord by the omnipotent power of the Holy Spirit, sacramentals are helps that predispose those who are already in a state of grace who use them properly to be more open to the grace of God. They produce grace through the Church's prayer to God as the body of Christ interceding for the salvation of the world and the protection and help of Christian believers.
Only certain sacramentals require a particular predisposition on the part of the person using them: Holy water, the Sign of the Cross, the blessed ashes of Ash Wednesday, the Rosary, praying the Liturgy of the Hours, personal attendance at Mass or the Divine Liturgy, praying the Lord's Prayer and the Psalms (such as the 23rd Psalm), devout reading of the Bible for a minimum of 15 minutes or more, visitation to a holy building, cathedral, church, shrine, monastery, chapel out of respect for a holy place and to pray there, having holy pictures and holy cards (pictorial representations of saints and angels on one side with a printed prayer on the other), the wearing of blessed objects and holy medals dedicated to the honor of saints as servants and representatives of Jesus Christ as their Lord and Savior, such as the Scapulars (Brown, Red, White, Blue, Black), and various medals, the Medal of the Immaculate Conception called the Miraculous Medal, promulgated by Saint Catherine Laboure, the medal of Saint Benedict and others, blessed candles, vestments, and reverential respect for the relics of the saints and for hallowed ground such as the site of a church or a cemetery blessed for Christian burial.Vatican II teaches:
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 kind, which are obtained through the Church's intercession. By them men are disposed to receive the chief effect of the sacraments, and various occasions in life are rendered holy
—SC 60 (Documents of Vatican II: Sacrosanctum Concilium Constitution on the Sacred Liturgy)
Only the Holy See alone, as representative head of the body of Christ as the earthly temple and representative of God, has authorization by apostolic succession to constitute new sacramentals and abolish, change, or interpret those already in use.