快刀

tā yòng kuài dāo bǎ guā qiē chéng kuài

她用快刀把瓜切成块。

She uses a sharp knife to cut the melon into sections.

nǐ xū yòng kuài dāo cái néng bǎ jié qiē duàn

你需用快刀才能把结切断。

You need a sharp knife to cut through the knot.