Abstract: An actuator, connectable to and for adjusting a device, comprises a housing having a longitudinal passage extending between first and second ends and defining an opening at or adjacent to the second end, and a spindle supported in the housing and movable longitudinally in the housing passage. The spindle has two oppositely handed, longitudinally spaced threaded first and second portions respectively nearer to the first and second ends of the housing. A first threaded nut fixed relative to the housing is threadedly engaged with the first threaded portion. A handle rotatably mounted at the first end of the housing is coupled to the spindle for rotating the spindle in the first nut and thereby moving the spindle longitudinally relative to the first nut and the housing.