Abstract: A rotor shaft of a steam turbine is provided with a dovetail-shaped groove. A plurality of inserts are received in the groove through an entry slot at a predetermined circumferential location. Each insert has a sealing surface which, when all inserts are disposed in the groove, form a continuous sealing surface about the rotor shaft. Pins are employed to retain the final insert and, hence, all inserts in the groove by connecting the final insert either to the rotor shaft or to adjacent inserts. In this manner, heat generated by the brush seal bristles bearing on proud portions of the rotor sealing surface is substantially uniformly distributed about the inserts prior to any heat transfer to the rotor. To the extent heat is transferred to the rotor, the temperature distribution is substantially uniform whereby bowing of the rotor due to differential circumferential heating by brush seal contact with proud portions of the rotor is avoided.