In plano: The Sanctuary level on which the Priest begins the Mass.
Predella: The level on which the Priest stands - e.g. during the Canon.
Secreto: Vocal but inaudible.
Per breviorem: The most direct way between any two given parts of the Sanctuary.
Per longiorem: Instead of going direct from one part of the Sanctuary to another, to go first to the middle of the Altar and bow (or genuflect), and then to proceed to the appointed place.
1. Servers and all others who are not wearing vestments always genuflect to the Blessed Sacrament, and to the cross when the Blessed Sacrament is not on the altar. Canons and those of higher ranks only bow to the cross.
2. If the Blessed Sacrament is in the Tabernacle, the Celebrant must make the 'usual reverence' - viz. a genuflection; if the cross only is on the Altar, the 'usual reverence' for the Celebrant consists in bowing the head and shoulders. At the beginning of a function, and on going to the Altar after the 'Gloria', 'Credo', etc., a profound bow is made.
3. On Good Friday, after the cross has been unveiled, all, without exception, must genuflect.
4. The prostration (genuflection on both knees and slight inclination of the head and shoulders) is only necessary on arriving at and departing from the Altar of Exposition or the Chapel of Repose.
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