A wooden mallet or pestle, especially the large one used for pounding mochi in a usu (mortar).
At New Year's, we pound mochi with a mallet and mortar.
I ground soybeans into powder with a pestle.
Standard kanji spelling; commonly used in contexts like mochi pounding.
Kana spelling is sometimes used in informal writing or when the kanji is not at hand.
The kanji 杵 is a phono-semantic compound: 木 (tree, wood) + 午 (a pestle shape). The reading きね is a native Japanese word of uncertain origin.