Prayer rope 100 knots with thick rat-tail thread.

A prayer rope or komboskini is a rope usually made of black wool or silk thread woven into knots. It is a prayer aid for monks, clergy, and laypeople of the Orthodox Christian religion. It can be worn on the wrist or have a long length, and its size is related to the number and size of the knots. It can have 33, 50, 100, 300, or more knots. 

Symbolism of the prayer rope: 

It is usually woven from wool to symbolize that all believers are the rational sheep of the Shepherd Jesus Christ, and it has a black color to symbolize the mourning of sins. It ends in a tassel whose purpose is to wipe away tears. The 33 knots symbolize the years of Jesus, the 99 are 33 multiplied by the number of persons of the Holy Trinity, and each knot is made of 9 woven crosses, symbolizing the nine orders of angels.