If such a rotor is supported on two knife edges, it would swing until the "heavy point" was facing downwards. This means this unbalance acts even without rotation; it is therefore called "static unbalance". It causes the centre of mass to shift away from the geometric centre, which in turn causes the rotor to swing oscillate parallel to its rotational axis when it is running.
Static unbalance should be corrected in the centre of gravity plane. This is achieved by removing material at the "heavy point" or attaching material at the opposite side. Correction of static unbalance in one correction plane occurs particularly frequently in disc-shaped rotors. Therefore, vertical balancing machines are usually the most suitable balancing machine for static unbalance measurement.