Is it appropriate to kneel when the tabernacle is opened? While we are saying the Lamb of God during Mass the tabernacle is opened, and we wait until the end of the prayer before kneeling. Also, where does it say we must kneel for the consecration?
Since liturgical law says that we should kneel after the Agnus Dei (Lamb of God), unless the local bishop has determined otherwise, that is what we should do. “The faithful kneel after the Agnus Dei unless the diocesan bishop determines otherwise” (General Instruction of the Roman Missal Including Adaptations for the Dioceses of the United States of America 43).
Regarding the posture during the consecration or Eucharistic Prayer, the GIRM says,
In the dioceses of the United States of America, they should kneel beginning after the singing or recitation of the Sanctus until after the Amen of the Eucharistic Prayer, except when prevented on occasion by reasons of health, lack of space, the large number of people present, or some other good reason. Those who do not kneel ought to make a profound bow when the priest genuflects after the consecration. (43)