This is an email I sent to the TPC congregation in October 2009 explaining why we have our baptismal font at the doorway into the sanctuary and why we do our baptisms from the location rather than from the front of the sanctuary. It has a few other details about liturgical practices that might be of interest.
You may notice that we do baptisms at the entrance to the sanctuary.
The placement of the baptismal font at the entry point of the sanctuary is not accidental. It serves an important symbolic purpose. Because baptism is the means by which we enter the church (as virtually all Christians agree; cf. 1 Cor. 12:13 and Westminster Confession 28.1), it makes good sense to keep the font there as a reminder of this truth. Each week as we enter the worship service, passing by the font helps us to remember that we are God's baptized people. We have access to God only because we have been cleansed by the blood of Jesus and have received the outpouring of God's Spirit in baptism. We are invited to draw near to God in the heavenly most holy place "having our hearts sprinkled from an evil conscience and our bodies washed with pure water" (Heb. 10:19-25). In baptism, God ordained us as members of his royal priesthood in Christ so that we are qualified to minister and offer sacrifice in his presence. We are clothed with Christ as our priestly garment (Gal. 3:27-28) and share in his anointing of the Spirit (Acts 2:33, 38).
Since baptism is our entry point into the covenant community, it makes sense to have the font and perform baptisms at the church's entrance. In this case, the layout of the church and biblical theology match and reinforce one another. This symbolic practice of performing baptisms at the church entrance traces back to the earliest Christians, and continues to be an architectural feature of many church buildings in many different Christian traditions in our own day. A Lutheran theologian makes the following remark:
While only a bowl is needed for baptism, the font is usually much more elaborate than that in order to emphasize the importance of baptism. Since baptism is the sacrament of initiation or entrance to the church, it is becoming much more common to place the font at the entrance...This position results in excellent symbolism. As worshipers enter church...they pass the font which serves as a visual reminder that we can come into God's presence because our sins have been washed away in baptism (Psalm 24: 3-4). Pushing the font off in a corner should be avoided. Because baptism is important the font should be substantial and have a prominent place of its own.
Liturgical theologian Ken Collins notes the origins of placing the baptismal font at the back of the sanctuary in the first house churches:
In a Roman house, the household’s water source was in the atrium just inside the front door. When early Christians converted a house to a church, that water source became the place where baptisms could take place if it wasn’t possible to baptize outdoors. Even though the position of the baptistery was determined by the existing architecture of the house, it took on a symbolic meaning, because baptism is the entrance to the Christian life.
If you've been in very many older church buildings or cathedrals, you have no doubt seen baptismal fonts placed near the sanctuary's threshhold. In keeping with this long and venerable tradition, we will do our baptisms at the entrance from now on. We know this will be a bit different than what most folks are used to -- and will also require people to crane their necks around to the back to witness the event. But such minor inconveniences are worth it in order to preserve such beautiful and deeply rooted theological symbolism.