Another method of binding the pages of a hardback case bound book is called “split pins”. Split pins have various colours. The pages would be collated, drilled and the pins will be inserted through, and then slid on. As you can see the are various lengths. The books could be up to one and a half inches thick. The back cover is simply full surface, glued, like the back cover of a block into the inside back cover of the hardback case. When the book is open you see the pins. If you want to add or subtract sheets, you simply move the two sliders. The prongs come in and out. This is another method where you bind sheets and then be able to add or remove them in a hardback case bound style.