The role of the subdeacon is to present the paten and the chalice to the deacon at solemn high Mass, to pour the water into the chalice, and to sing the Epistle. He is also responsible for purifying the sacred linens
The ceremonies of the ordination to the Subdiaconate take place as follows: after the admonitions concerning their definitive commitment, the ordinands prostrate themselves on the ground, face to the earth, as a sign of humility and adoration, as the patriarchs and prophets once did. Then, in unison with all the elect of Heaven, is sung the Litany of Saints, the favorite prayer of the Church in which all of the meritorious titles and the works of the God-Man are presented to the Holy Trinity. This prostration and litany precede the ordination to the diaconate and to the priesthood as well. Then the admonition to the ordinands lists out the functions of the subdeacon. There follow the tradition of the chalice the paten, and of the cruets, the prayer for the new subdeacons, and finally the imposition of the sacred vestments and the handing over of the book of Epistles.
From the begining of the ordination, the bishop warns the subdeacons that perpetual chastity is imposed upon them and that no one may be admitted to this order without the sincere will to accept celibacy (cf. Code of Canon Law 1917, can. 132). In order to allow the subdeacons to raise their mind regularly to God, the Church commands them to recite the breviary (Ibid., can. 135). Their new state demands of them a profound spirit of faith and the practice not only of purity of body but also of soul.
The bishop asks for the subdeacons the grace to fulfill their functions well, along with the gifts of the Holy Ghost, so that they may be the watchful guardians of the altar and of the holy Host during the sacrifice.