The rosary, or chaplet, is used in heraldry as an external ornament for those who are Professed Religious (men or women) and who are not also ordained to the priesthood. It is sometimes used by those who are officials and, therefore, entitled to use some other external ornament like a prior’s staff or even a crozier, in the case of Abbesses. The rosary is usually black and consists of five sets of ten beads, called decades, separated by five larger beads. It completely surrounds the shield and terminates at the bottom with three small beads and a cross.
The Prince and Grand Master of the Sovereign Military and Hospitaller Order of St. John of Jerusalem, Rhodes and Malta as well as professed knights of Justice of that order also make use of the rosary since they are actually Professed Religious in the Roman Catholic Church. However, they make use of a silver or white rosary that usually terminates in a Maltese cross.
Below is the coat of arms of the current Prince and Grand Master of the Order of Malta, His Most Eminent Highness, Frá Matthew Festing when he was Grand Prior of England which illustrates the use of the rosary well.