There are certain places in the liturgy where we are encouraged to make the sign of the cross (tracing the sign of the cross over ourselves from head to chest, and from shoulder to shoulder). Most frequently this occurs when we say the Triune name ("In the Name of the Father, of the Son, and of the Holy Spirit"), or when we give or receive blessings.

This is not some random act of superstition but rather a proclamation that all blessing and power and hope and victory and divinity come to us through nothing other than the Cross of Jesus (Gal.6:14).