Aspersion and affusion fonts
The fonts of many Christian denominations are for baptisms using a non-immersive method, such as aspersion (sprinkling) or affusion (pouring). The simplest of these fonts has a pedestal (about 1.5 metres tall) with a holder for a basin of water. The materials vary greatly consisting of carved and sculpted marble, wood, or metal. The shape can vary. Many are eight-sided as a reminder of the new creation and as a connection to the practice of circumcision, which traditionally occurs on the eighth day. Some are three-sided as a reminder of the Holy Trinity: Father, Son, and Holy Spirit.
Fonts are often placed at or near the entrance to a church's nave to remind believers of their baptism as they enter the church to pray, since the rite of baptism served as their initiation into the Church. In many churches of the Middle Ages and Renaissance there was a special chapel or even a separate building for housing the baptismal fonts, called a baptistery. Both fonts and baptisteries were often octagonal (eight-sided), octagonal fonts becoming more common from the 13th century and the rule from the 14th century. Saint Ambrose wrote that fonts and baptisteries were octagonal "because on the eighth day,[a] by rising, Christ loosens the bondage of death and receives the dead from their graves".
Saint Augustine similarly described the eighth day as "everlasting... hallowed by the resurrection of Christ".
The quantity of water is usually small (usually a litre or two). There are some fonts where water pumps, a natural spring, or gravity keeps the water moving to mimic the moving waters of a stream. This visual and audible image communicates a "living waters" aspect of baptism. Some church bodies use special holy water while others will use water straight out of the tap to fill the font. A special silver vessel called a ewer can be used to fill the font.
The mode of a baptism at a font is usually one of sprinkling, pouring, washing, or dipping in keeping with the Koine Greek verb βαπτιζω. Βαπτιζω can also mean "immerse", but most fonts are too small for that application. Some fonts are large enough to allow the immersion of infants, however.