It is a rosary-type device used by the Russian Old Believers and some Byzantine Catholics on which one may say either Hail Marys or "Lord Jesus Christ Son of God Have Mercy Upon Me the Sinner."
The focus of the Lestovka and the Prayer Rope, another Byzantine rosary-like devotion, is entrance into full communion with God's divine energies and his process of Theosis.
Good Post and Good Thread.
I have a solid devotion to "The Mother of God" and Our Lady has led me back to the practise of the Catholic Faith after I was quite indifferent for a period of time.