Diǎn tóu (-)
original: 点头
sign (mark) near the vibrating end of the reed tongue
From 点 [point] + 头 [head; top; end]; Its function is unclear to me (yet), but it could mark the spot where 红蜡 (hónglà [red wax]) is applied when tuning; NB: In the transrciption "diǎntóu" (i.e. without space) 点头 translates as "(to) nod (one’s head)".
张跃进 [Zhāng Yuèjìn]: 笙教学教程 [Shēng jiàoxué jiàochéng; Shēng teaching course], 北京 (Běijīng), 2012, p.3.
Wong, Samuel Shengmiao: Qi’ - An instrumental guide to the Chinese orchestra. Singapore, 2005, p.139 (hongla).
ws (linguistics [➺ Dictionaries, &c.])汉英词典 (Hàn Yīng cídiǎn) / A Chinese-English dictionary. 北京 [Běijīng], 1985, p.151 (点 ➁) & 692 (头 [1] ➂), and 279 [hóng] & 403 [là].