It is an important part because it sets a string and receives pressure from the string, and affects the good or ill of shooting such as the angle at which the boshi is set, the thickness, the form and so on.
弦を掛け、弦の圧力を受ける部分で、帽子の取り付け角度、太さ、形状等、行射の善し悪しに関わる重要な部位である。