A prayer rope (Greek: κομποσκοίνι, Russian: вервица, Romanian: mătănii, Serbian: бројаница, Bulgarian: броеница) is a loop of knots, usually made of wool but sometimes of wood, that is used during praying to keep track of the number of prayers which have been said.
The rope is usually used with 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 300, 50, or 33 knots or, less commonly, 250 or 12 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. "The purpose is to help us concentrate, not necessarily to count." 
Its invention is attributed to St. 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 with them, to remind them to pray constantly in accordance with St. Paul's injunction in I Thessalonians 5:17, "Pray without ceasing."
In some Russian Orthodox service books, certain services 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.
Another form of prayer rope was formerly in use in Russia, and is still preserved among the Old Believers. It is called lestovka ("ladder"), and is arranged asymmetrically. Whereas the more common 100-knot prayer rope is divided into four sets of 25 knots each, separated by larger knots or beads (dividers), the lestovka consists of counters consisting of loops of cloth or leather often containing short lengths of small-diameter dowel, arranged in groups as follows: 12 (for the number of the Apostles); 39 (for the weeks of the pregnancy of the Theotokos); 33 (for the years of Christ's life on earth), and 17 (for the number of prophets). These sections are separated by dividers larger than the counters, and there are three further divider-sized counters at each end, for a total of nine such large counters (for the nine ranks of angels); thus there are a total of 101 counters plus nine large ones. Where the ends join, they are sewn to four triangular leaves (for the four Gospels) sewn together two and two, the upper pair overlapping the lower. The lestovka is used with the Jesus prayer, but also for counting litany responses, which will often total 12 or 33; for this purpose it is better suited than the more familiar variety of prayer rope.
The prayer rope has many parallels among other religious groups. See w:Prayer_beads for details.
Previously, monks would count their prayers by casting pebbles into a bowl, but this was cumbersome, and could not be easily carried about when outside the cell. The use of the rope made it possible to pray the Jesus Prayer unceasingly, whether inside the cell or out.
It is said that the method of tying the prayer rope had its origins from the Father of Orthodox Monasticism, Saint Anthony the Great. He started by tying a leather rope with a simple knot for every time he prayed Kyrie Eleison ("Lord have Mercy"), but the Devil would come and untie the knots to throw off his count. He then devised a way--inspired by a vision he had of the Theotokos--of tying the knots so that the knots themselves would constantly make the sign of the cross. This is why prayer ropes today are still tied using knots that each contain seven little crosses being tied over and over. The Devil could not untie it because the Devil is vanquished by the Sign of the Cross.
Despite its wide usage among the Orthodox Christians (e.g. the Greek and Russian Orthodox), the prayer rope is unknown in many parts of the world. Even among Roman Catholics it is often mistaken for a rosary. Out of ignorance some even wear them on their necks.
- How to tie an Orthodox Prayer Rope knot
- How to Make a Prayer Rope video
- About Prayer Ropes from St. Luke Serbian Orthodox Church
- The Historical Development of the Orthodox Prayer Rope and its Importance to our Spiritual Life by Dr. Alexander Roman (Ukrainian)
- The Monk's Prayer Rope, taken from "Monasticism in the Orthodox Churches" by N.F. Robinson, 1964.
- Comboschini (The Prayer Rope): Meditations of a Monk of the Holy Mountain Athos
- The Prayer Rule of St. Pachomius
- What is the Prayer Rope and how to use it plus articles and links.
- The Orthodox Prayer Rope and the Jesus Prayer
- Saint Anthony the Great and the Prayer Rope