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knife attached to the sheath of a sword
「小柄」 has other readings with different meanings.
彼女は小柄だがとても力持ちである。
She is small but strong.
小柄な体格を生かしてダンサーになった。
I became a dancer taking advantage of my small build.
小柄な体格でも存在感のある人物だ。
Even though small, he is a person with presence.