The panel (1.5m x 2.0m) consists of a part of a board with sharp wane with fastening to each other, mixed with a planed board. Alder. Can be used anywhere including in a steam room.

Panel "Torn Tree" Alder with bark. Woodson.

https://woodson.ru/catalog/otdelka_dlya_bani_i_sauny_/panno_dlya_otdelki_ban/panno_rvanoe_derevo_olkha_s_koroy/