(as) useless as an ashtray on a motorbike

(as) useless as an ashtray on a motorbike

Utterly ineffectual or unnecessary. Primarily heard in Australia. Hey, thanks for the broken wrench—it's as useless as an ashtray on a motorbike. I know next to nothing about computers, so I'd be useless as an ashtray on a motorbike trying to figure out what's wrong with your laptop.
See also: on, useless
Farlex Dictionary of Idioms.
See also:
  • useless
  • (as) useless as tits on a bull
  • (as) useful as tits on a bull
  • (as) worthless as tits on a boar (hog)
  • (as) useless as tits on a nun
  • nun
  • (as) useless as tits on a boar hog
  • tits on a boar hog
  • a bag-of-spanners face
  • a face like a bag of spanners