A prayer rope (Comboschini) is a loop made up of knots, usually made of wool, that is used by Eastern Orthodox Christians and Eastern-Rite Catholics to count the number of times they have prayed the Jesus Prayer: "Lord Jesus Christ, son of God, have mercy on me, a sinner." Historically it typically had 100 knots, although prayer ropes with 50 or 33 knots can also be found in use today. There is typically a knotted cross at one end, and a few beads at certain intervals between the knots.
Its invention is attributed to Saint Pachomius in the fourth century as an aid for illiterate monks to accomplish a consistent number of prayers and prostrations. Monks were often expected to carry a prayer rope almost constantly, to remind them to pray constantly in accordance with Saint Paul's injunction in I Thessalonians 5:17, "Pray without ceasing."
In some Russian Orthodox service books, certain liturgies can be replaced at need by praying the Jesus Prayer a specified number of times, anywhere from 300 to 1,500 times depending on the service being replaced. In this way prayers can still be said even if the service books are unavailable for some reason. The use of a prayer rope is a very practical tool in such cases, simply for keeping count of the prayers said.
According to a popular legend, the prayer Rope has its origins from the Father of Orthodox Monasticism, St. Anthony. He started by tying a leather rope for every time he prayed his Kyrie Eleisons, or Lord have Mercies, and the Devil came and would untie it to throw his count off. He then devised a way, inspired from a vision by the Theotokos (Mother of God), of tying the knots so that the knots would constantly make the shape of the cross. That is why Prayer Ropes today are still tied by little crosses being tied over and over. The Devil could then not untie it because the Devil is vanquished by the sign of the Cross.