A method is described for improving the sealing between rotor and a plurality of blades. The rotor has a plurality of generally axially extending profiled recesses into which a ring of blades, which have corresponding blade root profiles, are inserted in a form-fitting and/or frictionally locking manner into these recesses in a generally axial insertion direction. Between the recesses the rotor has tangential surface sections or circumferential surface sections which extend in the axial direction and circumferential direction and are generally indirectly covered by lower shrouds of circumferentially adjacently arranged blades in the radial direction. At least one of the tangential surface or circumferential surface sections is provided with a step in the radial direction, and a corresponding recess, which adjoins as flush as possible, is provided in the underside of the shroud of the blade which is arranged above it. Corresponding rotors or blades are also described.