Tsuno' (a core material which is a thimble-like wood or horn of water buffalo and so on, which is hollowed out) is put inside of boshi (thumb), and the tip of thumb covered with it has no degree of freedom.
帽子（親指）に「角（木、或は水牛等の角を指筒状に刳り貫いた芯材）」が仕込まれており、それに覆われた親指先の自由度は全くない。