It is a model of the very useful thumb book dividers, it is as simple as putting your thumb in the hole and grabbing the book, it will prevent the pages from closing. As a reader I can say that despite the simplicity it is very useful. It's done in the Inventor program and the images were rendered in Blender. There are several with various sizes, from very small to large size. If you require one with more specific dimensions or with another design of your liking you can contact me without hesitation. If there is a mistake with the files in the same way contact me, I can't always respond as quickly as I would like, but I always respond. I would love to see the makes they make of the model. <3