For physical books, like many others here, I use whatever comes to hand. I used a plastic flossing stick most recently.
I don’t dog-ear books any more; neither do I write in them unless it is a textbook for some class (not done that in 40 years).
I don’t dog-ear books any more; neither do I write in them unless it is a textbook for some class (not done that in 40 years).