fit on

fit on (something)

To attach or place something onto something else. A noun or pronoun can be used between "fit" and "on." I can't fit on these gloves—are you sure they're mine? You know, you can adjust that wrench if you can't fit it on the nut.
See also: fit, on
Farlex Dictionary of Idioms.

fit something on(to) something

 and fit something on
to manage to place something onto something. See if you can fit this lid onto that jar over there. Sorry, I can't fit on this lid, because it's too big.
See also: fit, on
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • fit on (something)
  • fit out
  • You cannot get a quart into a pint pot
  • you can't get a quart into a pint pot
  • fit in with (someone or something)
  • serve the purpose
  • serve a purpose
  • give (someone) a fit
  • give someone a fit
  • fiddle