“From the time of Tertullian Christian writers testify to the use of the ‘sign of the Lord’, partly as sanctifying every action in daily life from rising in the morning to retiring at night, partly as an encouragement in temptation and trial, and partly as a means of mutual recognition in times of persecution. From early times the sign was also employed in Baptism and Confirmation, and its use was then extended to the liturgical blessing of persons and things. In the early centuries the sign was drawn upon the forehead by the thumb or finger of the right hand. In later times it has been made by drawing the right hand from the forehead to breast, and then from shoulder to shoulder. It is usual in the Western Church to make the cross-stroke from left to right, in the East from right to left”.
The article in The New Westminster Dictionary of Liturgy & Worship also has a good discussion about the sign of the cross and notes that “the sign of the cross may be made over persons or things. It may be self-administered or directed towards others”.
1. From “Sign of the cross” in The Oxford Dictionary of the Christian Church. Edited by F.L. Cross. 3rd edition edited by E.A. Livingstone. Oxford: Oxford University Press, 1997. p. 1500.2. From “Gestures, 2. Signing with the Cross” by Jeremy Haselock in The New Westminster Dictionary of Liturgy & Worship. Edited by Paul Bradshaw. Louisville: Westminster John Knox Press, 2002. p. 228.