A small square rug for the hands and head to be kept clean when bowing to the ground for pious Orthodox Christian believers. The size of the side of this square ranges from 30 to 40 cm. Felt, cotton, and wool are placed inside. All of this is quilted.
Symbolism:
Square - Earth
4 (triangles within a square) is the number of Evangelists.
5 (squares) - the number of wounds of Christ
7 (concentric squares) - the number of Councils and Sacraments.
9 (squares) - the number of Angelic ranks and Beatitudes.
12 (triangles: 4 squares one in the other) - the number of Apostles.
The prayer rug can also be "simple", i.e. not from triangles of different fabrics, but from one square piece. After all, its main purpose is not to remind the worshipers of the number of Ecumenical Councils, Gospels, etc.
A demonstration on how the prayer rug is used can be seen in the following video from 10:46 to 11:10:
https://yandex.com/video/preview/12059730243289812723