Why do we genuflect and when is the proper time to do it?  

Q: When I was in grade school, the nuns taught us to double genuflect (both knees) when leaving church after Holy Thursday Mass.

I took my children to all of Holy Week services. On Good Friday the sanctuary did not have the consecrated hosts in the tabernacle. The altar, of course, was bare. Do we genuflect anyway out of love and reverence to our Lord? Some parishioners did nothing upon entering the pew. What is right?

A: The double genuflection at certain times of the pre-Vatican II liturgy is no longer required by the rubrics of the new liturgy.

Some individuals or countries may continue it out of piety and devotion.

According to Msgr. Peter J. Elliot in Ceremonies of the Modern Roman Rite (Ignatius Press), genuflection on one knee is reserved for: 1) Our Lord present in the Eucharist on the altar, in the tabernacle, monstrance or pyx; 2) the cross during its veneration on Good Friday until the beginning of the Easter Vigil; 3) a relic of the true cross exposed for veneration.

A bow of the body (deep bow from the waist) is made to the altar if the Blessed Sacrament is not on it or behind it. A bow of the head is to be made at the mention of the three Divine Persons, at the names of Jesus and Mary and the saint in whose honor the liturgy is being celebrated.