You may have seen a grandparent use a κομποσχοίνι (prayer rope) or gotten a small woollen bracelet as a souvenir from a monastery and thought what's all that about?
The use of prayer ropes in the Orthodox faith goes so far back that we don't know the origins. There is an old legend that tells of a monk who decided to make knots in a rope, which he could use in carrying out his daily rule of prayer. But the devil kept untying the knots he made in the rope, frustrating the poor monk's efforts. Then an angel appeared and taught the monk a special kind of knot that consists of ties of interlocked crosses, and these knots the devil was unable to unravel.
The prayer rope is a purely practical tool. It is used to keep the hands busy and find focused while a person is meditating on a prayer. A person moves their fingers along each knots on the rope as they repeat their prayer.
Prayer ropes come in all shapes and sizes, ranging from 33 knots to 300 knots. The most common are 33 knots, the number of years Christ lived on earth.
There are two ways we can pray using the prayer rope:
1. We can discretely use the prayer rope in our left or right hand, and move from knot to knot while meditating upon the prayer: "Lord Jesus Christ have mercy on me" or "Most Holy Theotokos save us". This can be done throughout the day but it's important to do so secretly - God expects our prayers to be done without the attention and reward of other's.
2. At the time of our regular prayer, when we pray following the rule of prayer that our spiritual father has suggested to us, we hold the prayer rope with our left hand between the thumb and the index finger and move from knot to knot. At each knot we simultaneously do two things: i) with our right hand we make the sign of the cross over ourselves and ii) we say the prayer "Lord Jesus Christ have mercy on me". When we finish with all the knots of the prayer rope, we can continue following the same procedure, for as many times as our spiritual father has advised.
The prayer rope itself doesn't hold any special power. It's simply a tool that we can make use of. Monastics and laity use it alike to help meditate while praying.