It has been the custom in ecclesiastical heraldry for a bishop to join his personal arms with those of his diocese. The arms of the Diocese of Pittsburgh, shown on the left side of Bishop Wuerl's shield, were designed by the late Pierre Chaignon la Rose and show a black field on which are placed a blue and white chequy bar, a sword, and two crosses, all gold. The sword was added in honor of St. Paul, the titular of the Cathedral of Pittsburgh. In less technical terms, Bishop Wuerl's personal arms, which he has borne since his elevation to the episcopacy in 1986, show on a red field a gold tower, upon which a red globical convexed cross is placed. The symbols of Bishop Wuerl's personal arms represent a rich religious and historical background and significance.
Gold is the emblem of the sun, and of divinity.
The single-traversed gold processional cross behind the shield is a sign of episcopal rank. It is the one emblem in ecclesiastical heraldry that is reserved to bishops.