brian elliott:
Whenever one crosses before the tabernacle, and when not in procession, one always genuflects.
Here is the scoop on genuflecting and bowing:
- A genuflection, made by bending the right knee to the ground, signifies adoration, and therefore it is reserved for the Most Blessed Sacrament, as well as for the Holy Cross from the solemn adoration during the liturgical celebration on Good Friday until the beginning of the Easter Vigil.
During Mass, three genuflections are made by the priest celebrant: namely, after the showing of the host, after the showing of the chalice, and before Communion. Certain specific features to be observed in a concelebrated Mass are noted in their proper place (cf. above, nos. 210-251).
If, however, the tabernacle with the Most Blessed Sacrament is present in the sanctuary, the priest, the deacon, and the other ministers genuflect when they approach the altar and when they depart from it, but not during the celebration of Mass itself.
Otherwise all who pass before the Most Blessed Sacrament genuflect, unless they are moving in procession.
Ministers carrying the processional cross or candles bow their heads instead of genuflecting.
- A bow signifies reverence and honor shown to the persons themselves or to the signs that represent them. There are two kinds of bows: a bow of the head and a bow of the body.
A bow of the head is made when the three Divine Persons are named together and at the names of Jesus, of the Blessed Virgin Mary, and of the Saint in whose honor Mass is being celebrated.
A bow of the body, that is to say a profound bow, is made to the altar; during the prayers Munda cor meum (Almighty God, cleanse my heart) and In spiritu humilitatis (Lord God, we ask you to receive); in the Creed at the words Et incarnatus est (by the power of the Holy Spirit . . . made man); in the Roman Canon at the words Supplices te rogamus (Almighty God, we pray that your angel). The same kind of bow is made by the deacon when he asks for a blessing before the proclamation of the Gospel. In addition, the priest bows slightly as he speaks the words of the Lord at the consecration.
Hope this helps!