I finally made it: an XOR mechanism that requires exactly one of two keys to be inserted at a time. I call it the 🗝️ #keyguardian.
This is very useful for example to track where important small things go: Want to take the car keys? You have to insert your name tag to unlock it.
My first mechanical project with #SolveSpace and it was great!
EDIT: Now on #Printables: https://www.printables.com/model/793767-keyguardian-dual-key-xor-mechanism
@nobodyinperson This is delightful!
May I make a suggestion for a version two, because I have one?
@nobodyinperson The two types of keys appear to have the same kind of latching ends, which means potentially you could end up with someone using a name key to remove and replace another name key, while not returning the borrowed object.
If, however, the name keys were keyed differently to the object-holding keys, this wouldn't be possible.
I think you could invert the keying on the name keys (or the object key doesn't matter) and still have it all fit in a package of the same size.
Yann Büchau 
Solarbird 
James Just James