A prayer rope (
Historically, the prayer rope would typically have 100 knots, although prayer ropes with 150, 50, or 33 knots can also be found in use today. There are even small, 10-knot prayer ropes intended to be worn on the finger. Hermits in their cells may have prayer ropes with as many as 300 or 500 knots in them.
There is typically a knotted
The prayer rope is commonly made out of wool, symbolizing the flock of Christ;  though in modern times other materials are used also. The traditional color of the rope is black (symbolizing mourning for one's sins),  with either black or colored beads. The beads (if they are colored) and at least a portion of the tassel are traditionally red, symbolizing the blood of Christ and the blood of the martyrs. In recent times, however, prayer ropes have been made in a wide variety of colors.
Though prayer ropes are often tied by monastics, lay persons are permitted to tie them also. In proper practice, the person tying a prayer rope should be of true faith and pious life and should be praying the Jesus Prayer the whole time.
According to Orthodox Serbs, the 33 knotted prayer rope should be worn on the left hand, and when praying, held with the thumb and forefinger of the right hand. The 33 knots symbolize the age of Jesus Christ when he was crucified. 
Among the Oriental Orthodox, the prayer rope is composed of 41, 64, or 100 beads and is primarily used to recite the Kyrie Eleison prayer as well as others such as the Lord's Prayer and the Magnificat. In regards to the first two numbers, the former represents the number lashes inflicted on Jesus (39 according to Jewish custom), the lance, and the crown of thorns, while the latter represents Mary's age upon her Assumption respectively.