Prayer ropes are commonly made with knots and used to keep attention during repeated prayer. Many Orthodox Christians use them while praying the Jesus Prayer: Lord Jesus Christ, Son of God, have mercy on me, a sinner.
Why use one?
The rope gives the body something quiet to do and helps the mind return when it wanders. It can support a small prayer rule, especially when a person is trying to pray regularly without constantly checking a clock or screen.
Use with humility
The point is repentance and remembrance of God, not quantity. Counting prayers can become unhelpful if it turns into pride, anxiety, or spiritual comparison. A small number prayed attentively is better than a large number prayed mechanically.
Ask for guidance
Repeated prayer can be very simple, but more intense practices should be undertaken with pastoral guidance. The Orthodox tradition is careful because prayer involves the whole person.
If using a prayer rope leads to anxiety, pride, or obsessive counting, simplify the rule and speak with a priest or spiritual father.