Bookbinders can incorporate leather jointed endpapers into books as a decorative element, but they also separate the free endpaper from the pastedown. This opens up a number of possibilities in design and materials, for example having decorative doublures on the inside of the boards. There are many ways to make a leather jointed endpaper - this is just one. Hopefully you will be able to adapt the endpaper construction if necessary to suit your own needs.