For use in a printing press cylinder (1) of the type having in its surface an axial cavity (2) produced for location of a lock-up device for a printing blanket on the cylinder, there is provided an adaptor fillet to adapt the cylinder for accommodation of a printing blanket without a lock-up device, the adaptor fillet comprising a fillet (3) of a shape for insertion into the cavity so as to bridge the cavity flushly with the cylinder surface periphery, said fillet having an arcuately curved bridge surface (10) of the same radius of curvature as that of the cylinder and having in its bridge surface a longitudinal slit (11) for guidance of a knife edge. In a preferred embodiment of the invention, the fillet is in two-part form, consisting of a lower part (4) securable in the cavity by a threaded fastener entering the cavity base, and an upper part (5) securable to the lower part and providing the arcuately curved bridge surface. The adaptation enables an existing lock-up type printing cylinder to be adapted for non-lock-up securement of a printing blanket without removal of the cylinder form the press, and provides a cylinder surface suitable for application of an adhesive-backed blanket.