Q: When the Bishop celebrates Mass, and there are many deacons in the entrance procession, where do they line up in relation to concelebrating priests?
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A: It depends on what the deacons are doing. The Ceremonial of Bishops imagines that deacons fall into three categories: one who carries the Book of the Gospels, two more who assist the bishop, and everybody else.
The one with the book of the gospels follows the other servers and non-concelebrating clergy. Then the deacons without a specific function enter two by two. The concelebrants follow them, two by two. And the two deacons who assist the bishop walk a little behind him.
In the United States it’s been customary for the two deacons assisting the bishop to divide their roles as the deacon “of the Word” and the deacon “of the eucharist”—the first taking roles during the first part of the Mass, and the other taking roles in the second part. But the Ceremonial envisions three deacons. It is vague, but it appears that the deacon who carries the Book of the Gospels also proclaims the gospel, and the other two deacons remain at the bishop’s side taking turns assisting him throughout.