A quantity of holy water is typically kept in a font, an item of church architecture that typically appears in a baptistery; a smaller font, called a stoup, may be placed near the entrance of the church. Roman Catholics bless themselves when entering the church by dipping their fingers in the holy water and making the sign of the cross. Holy water is also sometimes sprinkled upon the congregation during the Mass; this is called aspersion.
In the theology of Roman Catholicism, holy water is a sacramental, a "sacred sign which bear(s) a resemblance to the sacraments." Holy water recalls the sacrament of baptism.
The ritual of consecrating holy water traditionally is performed on Holy Saturday and during the vigil of Pentecost. Once consecrated, more ordinary water can be added to the supply of holy water, and the entire quantity of water remains consecrated provided that the amount added is less than the amount of water that was there. Holy water can in fact be consecrated upon any day in the liturgical calendar except Easter Sunday and Pentecost itself.