Abstract: Stabilization apparatus for a tower crane or other mobile equipment includes several telescopic structures.Each structure includes an inner telescopic part and an outer telescopic part and an actuator for moving the parts to a fully extended position. The inner telescopic part carries a plate which is applied in use to the ground and is controlled by a secondary telescopic structure.When the main telescopic structure is extended there is some sag so that a detector intended to indicate achievement of the extended position is not actuated. When the secondary telescopic structure is actuated and the plate is in firm contact with the ground the sag is corrected and the detector is actuated.