right down alley

(right) down (one's) alley

Something that one is or would be very interested in. A variant of the more common phrase "(right) up (one's) alley." Lou loves baseball, so you should definitely invite him to a game—it would be right down his alley. I love science, so studying medicine is down my alley.
See also: alley, down
Farlex Dictionary of Idioms.

right down someone's alley

 and right up someone's alley
Fig. ideally suited to one's interests or abilities. Skiing is right down my alley. I love it. This kind of thing is right up John's alley.
See also: alley, down, right
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • alley
  • (right) down (one's) alley
  • be (right) down (one's) alley
  • if it ain't broken, don't fix it
  • if it isn't broke, don't fix it
  • if it isn't broken, don't fix it
  • a nod is as good as a wink to a blind bat
  • a slue of (something)
  • champ at the bit
  • champ at the bit, to