How do you mark your physical books? What’s the strangest method you have heard to mark a book?

I usually rip out a little section of one of the blank pages in the back of the book and use it as a little bookmark, rather than dog-earing the page (only if it's my book!) like this: https://imgur.com/a/yQsLKKK

I had an uncle who would read books by finishing a page and then tearing it out and throwing it away. Not sure what that was all about!

But I was just curious to have a discussion about how we save our places in books. I wondered if anyone did anything else unusual or interesting. I hope this complies with the rules!