While researching for my book on the history of robots, I went to the rare book book of my local university library because they had an extremely rare copy of a 19th century boy’s weekly magazine about an inventor’s Steam Man. It was printed on newsprint and quite fragile. I took it into the reading room and started taking notes. I turned the page and was lost. Took me a moment to realize I was reading page 4 instead of page 2. The copy had never been cut. I had to bring it back. There was only a student at the desk and she had to find a librarian to open it up, which meant I had to come back at another date.
When I did, I went back to the reading room and excitedly turned the page. And was lost again. Sure enough, I was on page 4. The librarian dutifully cut the side that had been folded. But not the top of the page. I took the still unreadable copy back to the desk. Where a different librarian used the edge of a business card to cut it.
No collector would do that to a book, since modern collecting is all about getting copies in as close shape to the first copy ever printed as possible. But for a library an uncut book is unresearchable and research is their business. The edge of a stiff card is perfectly acceptable as a knife in such a situation. Ragged edges were the norm in those days and a perfect sharp cut was unnecessary overkill.