Abstract: A filler member for a rotor of a turbomachine in which the rotor is of the type comprising a body provided with a peripheral groove. Each side of the groove has a flange which has a surface facing radially inwards. A circumferential array of blades, each of which has a root shaped to engage the inward facing surfaces of the flanges and is capable of sliding along the groove. At least one of the flanges has a first recess therein to enable the blades to be loaded into, and removed from the groove. The filler member comprises, a base portion extending along the groove below the roots of one or more of said blades and has at least one tab connected to the base portion extending outwardly therefrom. The tab is movable relative to the base portion between a first position in which the tab is clear of said first recess and thereby allows the filler member to move along the groove and a second position in which the tab is located in the recess and so prevents said filler member from moving along the groove.