Milk bucket under a bull

I need to find a quote as witty and funny as "A woman needs a man like a fish needs a bicycle".

In the context of "its as much use to us as......... is to a ...........

Can anyone help?

Thanks

I'm told that a common farm expression is "About as useful as teats on a boar hog".

Useless as a screen door on a submarine.

A couple from This Dog'll Really Hunt: An Entertaining Texas Dictionary by Wallace O. Chariton (Wordware Publishing, Piano, Texas, 1989, 1990):

Useless as a cowboy without a horse.
...a milk bucket under a bull.
...a saddle without a horse.