When to approach the Communion rail?

When exactly are the faithful supposed to approach the Communion rail? Immediately after the priest genuflects after receiving the Host, immediately after he genuflects after receiving the Precious Blood, at the second _Confiteor_, immediately after the _Misereatur vestri_, or immediately after the _Ecce Agnus Dei…Domine non sum dignus_? I've seen choristers approach it immediately after he genuflects after receiving the Precious Blood, elderly people approach it immediately after the _Misereatur vestri_ (because it takes them longer to walk to the rail), and all other parishioners immediately after the _Ecce Agnus Dei…Domine non sum dignus_. Surely there are rubrics on when the faithful should approach the rail, aren't there? John Nolan commented on a ["Fr Hunwicke's Mutual Enrichment: The Roman Rite of 1965" blog post](https://liturgicalnotes.blogspot.com/2016/08/the-roman-rite-of-1965.html#c1198683246131737317) : > No-one ever approached the rail until after the _Ecce Agnus Dei_. From 1967, when the _Ecce_ preceded the priest's Communion (as in the *Novus Ordo*) a bell was rung to signal the people to approach the rail. That is probably why some people nowadays interpret the three bells at the priest's _Domine non sum dignus_ (wrongly) as a signal to come forward.