The specialized sacristy itself did not become part of church architecture until the 16th century, when it was often placed on the north side of the chancel, or choir, of a cruciform church (one in the shape of a cross). Later the position became less specific, the only requirement being that the room be accessible from both the sanctuary and the nave and sometimes from outside the church. In modern Protestant churches, in which it is generally called the vestry, its size and position vary greatly. Often it is situated between the residence of the clergy and the church itself.