VATICAN CITY (CNS) — Hours after the last visitors and pilgrims left St. Peter’s Basilica for the day, a chisel clanged and dust flew as a group of prelates chanted their prayers before a simple wall marked with a cross.

In preparation for the opening on Christmas Eve of the Holy Door in St. Peter’s Basilica, Cardinal Mauro Gambetti, the archpriest of the basilica, led the brief prayer service and ritual late Dec. 2.

As the cardinal and other priests prayed, workers broke into the wall that has sealed the Holy Door shut since the Jubilee of Mercy ended in late 2016.

The workers removed a metal box, tied with a ribbon and sealed with wax, that contains the handles and the key to the Holy Door as well as Vatican medals, documents about the last Holy Year and four gold-covered bricks.

As the clergy sang the litany of saints, Cardinal Gambetti led them in procession to the altar over the tomb of St. Peter and paused for a moment of prayer.

In a formal meeting room, the metal box was set on a table in front of Cardinal Gambetti, Archbishop Rino Fisichella, pro-prefect of the Dicastery for Evangelization, and Archbishop Diego Ravelli, master of papal liturgical ceremonies.

The workers pried open the box and unnailed another inside it, revealing its contents.

After Cardinal Gambetti signed a document attesting to what he found, Archbishop Ravelli took custody of the box to deliver it to the pope, the Vatican press office said.

Similar ceremonies were planned to prepare the Holy Doors of the Basilica of St. John Lateran Dec. 3, St. Paul Outside the Walls Dec. 5 and St. Mary Major Dec. 6.