295. The sanctuary is the place where the altar stands, where the word of God is proclaimed, and where the priest, the deacon, and the other ministers exercise their offices. It should suitably be marked off from the body of the church either by its being somewhat elevated or by a particular structure and ornamentation. – General Instruction of the Roman Missal
Here the Church requires that the sanctuary be marked off, calling for, yes, even now, a particular structure; in other words, an altar rail. The altar rail serves beautiful symbolic and considerately
Firstly, we call it an altar rail; the name has reference to the altar. This rail can be seen as an extension of the altar. Christ becomes present on the altar and invites us to be fed at His altar via the rail. Very often the appearance of the rail matches the appearance or imitates the appearance of the altar. In churches where there is no rail, this symbolism is very diminished or completely destroyed. There is a beautiful parallel in the series of events that lead to the distribution of Holy Communion. Just as the priest goes to the altar, offers the sacrifice, and brings that Sacrament to the altar rail for the faithful, so every Christian is called to Sunday Mass, called to the altar, and, nourished by that Sacrament, is sent out to bring Christ and His gospel to the world through daily life.
Practically, the rail is a help to people, both physically and spiritually. The use of rail and the way Holy Communion is distributed with it sets a solemn pace for the reception of Holy Communion. On the part of the priest, more of his time is spent actually distributing the BlessedSacrament and less time waiting. On the part of the person receiving, the hurried tone is removed; there is a great opportunity for quiet and prayer both a few moments before and after receiving our Lord. The rail also is a help to people in kneeling and standing back up.
On the psychological level, we all have a desire, built into us by God, to offer Him our love and worship, but all of our efforts will be imperfect. This is a truth we cannot escape. If we deny our short-comings and wrong-doings on our conscious level, we will feel it and suffer on a more subconscious level. Because we know that the ‘sanctuary‘ exists — we know that there is a realm that we are unworthy and unable to enter on our own. We know that our knowledge and power are limited. God, of course, knows this too and created a solution. God sent His Son — His Christ — as the perfect high priest, who in turn instituted the Sacrament of Holy Orders, by which He allows and commands men to enter His sanctuary and offer His perfect sacrifice, so that we, the entire Church, may join our imperfect sacrifices to His. Having a sanctuary that is marked off by an altar rail is not a way of keeping people out of where they have a right to go, but it is more than anything a visible reminder to us of the reality of our situation — we need God to do what we cannot. Our worship of God is not something that we get together and decide to do; it is something that God enables us to do. We cannot worship perfectly, so Christ enables us to join in His perfect act of worship.
The distinct sanctuary and the altar rail are, far from being something restricting, a symbol of a truth that is truly liberating — we need God. With reception of Holy Communion at the rail, we see the second part of that truth — God comes to us. We cannot reach God by our own powers, so He comes to us. Deep within us, we know the first part; we know we need God. If we deny this consciously, we will become a people of sadness, anger, and despair. Is it any wonder that a society that has rejected its need for God is full of people weighed down with despair, depression, and struggles of self-worth? It is precisely by acknowledging that we need God, as the sanctuaryand rail remind us, that we are able to acknowledge the joyful truth that God comes to us and thus become people of light, peace, and hope.
– Father Evan Harkins