The Work of the Sacristan
They are not always very obvious but they are not invisible either. Such is the liturgical role of the Sacristan within a parish.
Many parishes have a Sacristan, but some do not. But even in those parishes that have one, the Sacristan’s duties may seem mysterious to some observers.
The General Instructions of the Roman Missal describes the Sacristan’s role in Chapter III: Duties and Ministries in the Mass, in a single line
105. A liturgical function is also exercised by:
a) The sacristan, who diligently arranges the liturgical books, the vestments, and other things that are necessary for the celebration of Mass.