I have already run into four thousand problems with my doorknob idea.
They are not the problems I assumed I would have.
I assumed that, because I was buying vintage doorknobs, I might have a problem fitting them onto my modern doors, which already have holes and whatnot cut out to support the existing doorknobs. So I measured once, then measured again, then chuckled to myself because I figured I was beating some system and as long as the math added up, I'd be fine.
Welp - totally forgot about the different doorknob types.
There are passage/dummy doorknobs, which exist only to pull or push open a door, and have no locking mechanism. There are privacy doorknobs, which do have a locking mechanism. There are more types, but these two are sufficient detail for the problem I've encountered with my beautiful vintage doorknob set. It arrived today.
It does not have a locking mechanism, and I only have exactly what you see above. You see, that vintage doorknob is designed to be used with an actual key. See the keyhole? It's not decorative. It once worked.
Therefore, the interior fittings do not have the locking thingie that goes in the doorjamb. I have no single doors that are passage only and don't require a lock. Not a single one. I have two sets of french doors, one of which has passage doorknobs, but...the set above is not just passage. The knobs have that... stick thing... that needs to go into a hole in the door. And I'm not sure I'm up to the task of carving out a doorknob hole, plus it would leave raw metal sticking out one side if I tried to divide the set to use on both doors.
If this is not making any sense, it's because I need to go to bed. Bah, humbug.