double (up) as something
phrasal verb with double verb [ I or T ] uk/ˈdʌb.əl/ us/ˈdʌb.əl/
也可用作，还能当作
to be also used as something else
The kitchen table doubles as my desk when I'm writing. 我写东西时这个餐桌还可以当书桌用。
Our spare bedroom doubles up as an office for Dan when he's working at home. 丹在家工作时我们的备用卧室可以给他当工作间用。