I am trying to come up with a word that means something is intended to be used with something else, like "proprietary" without the legal connotation, for example after-market car parts. They're not proprietary, but they will only fit an '89 Cutlass, etc.
"Intended" is too broad, "integrated", "co-engineered", "related", "matching", "custom" all miss the mark.
"The Widget Co fasteners only work with these hinges, they're proprietary".
Edit more info:
Thanks FumbleFingers for "dedicated to/specifically made for", that is the right idea. I want to boil it to one word (if it's out there) to use in as a bullet point or - if I'm lucky - a mnemonic.