Giving multiple users permissions to the same file.

[iwO]

I can't give permissions to multiple users.
In User1's account, I change them to "User1: Read & Write, User2: Read & Write" Then, I log out and log in to User2's account only to find that it has changed to "User1: Read & Write, User1: Read & Write".
If I then change them back to: "User1: Read & Write, User2: Read & Write", the next time I log in as User1 I find that it has changed to "User2: Read & Write, User2: Read & Write".
Is there a way to give both users permissions?

 

[benwiggy]

Put the files in /Users/Shared.