When you ask a question about a quote you should give the entire sentence, so we can understand the context.
Here is a possible sentence using your words:
- It wasn’t possible to put a cigarette paper between his views and those of his friend.
It means that his views and the views of his friend were almost exactly the same.
You couldn't put something as thin as a cigarette paper between them.
If you can't put a cigarette paper between two people or two things it means that they are almost the same.....or that they are very close.