a telescopic actuator has a lead screw and one or more concentric or tiered screws . each screw has one or more tangential interference stop features such as stop cogs . as the lead screw is rotated , it translates out of the concentric screws . as the lead screw reaches its maximum extension , a tangential interference stop feature on the lead screw tangentially contacts a tangential interference stop feature on the concentric screw with which the lead screw is threadably engaged . upon tangential contact , the associated concentric screw rotates in unison with the lead screw . when there are additional concentric screws , as each concentric screw reaches its maximum extension , the system of tangential contacting of tangential interference stop features causes the other concentric screws to extend out in sequential fashion .