Strap hinge are pieces of white cardstock with binding to put them in the book, You can purchase clear page protectors, but they go on via the side. They are not the type that you do a page and slide it into the top of the clear protector. Those are postbound or 3 ring. HTH
In the old strap hinge albums I have, I had to cut the background papers down to fit between the page edge strips then glue them in. They were the first albums I bought. I've since changed to the three-ring type. Much better, I think.