A term applied to various manual acts, liturgical or devotional
in character, which have this at least in common: that by the
gesture of tracing two lines intersecting at right angles they
indicate symbolically the figure of Christ's cross. Most
commonly and properly the words "sign of the cross" are used of
the large cross traced from forehead to breast and from shoulder
to shoulder, such as Catholics are taught to make upon
themselves when they begin their prayers, and such also as the
priest makes at the foot of the altar when he commences Mass
with the words: "In nomine Patris et Filii et Spiritus Sancti".
(At the beginning of Mass the celebrant makes the sign of the
cross by placing his left hand extended under his breast; then
raising his right to his forehead, which he touches with the
extremities of his fingers, he says: In nomine Patris; then,
touching his breast with the same hand, he says: et Filii;
touching his left and right shoulders, he says; et Spiritus
Sancti; and as he joins his hands again