Pastedown
The pastedown is the half of the endsheet that’s glued to the inside of the book’s cover. It’s the part you see when you open the front or back cover. Unlike the flyleaf, it’s not loose and it’s permanently glued to the cover’s inner board. Printers usually call the front pastedown Cover 2 and the back pastedown Cover 3.
More on Endsheet, Pasteddown and Flyleaf
A red arrow pointing to the pastedown, which is the left side of an endsheet