A method and apparatus for exchanging an application roller which is aligned with a duct roller used to apply glue to a spine of a book block by rolling off the book block spine. The duct roller removes glue from a glue container to transfer glue to the application roller. At least two application rollers are arranging spaced apart, relative to each other, with one of the application rollers being positioned aligned and in contact with the duct roller. The duct roller and the at least two application rollers each have an axis of rotation that is positioned substantially normal to the conveying direction. The application rollers are moved in an axial direction with the aid of an exchanging device, such that a second one of the application rollers is moved into alignment with and against the duct roller in place of the first application roller.