body 80 the ridges 110 may further be provided with any desired width and or height of extension off of the surface of the periphery of the plug body 80 the height width and other characteristics of the ridges 110 if employed may be selected to provide a desired amount of holding force generation by the interference fit when the retained part 30 is being held in place by the captured part 20 furthermore in some cases the ridges 110 may be provided on internal portions of the sidewalls 70 instead of being provided on the plug body 80 as indicated above the retained part 30 may be insertable into or may be withdrawn from the reception sleeve 40 when the capturing part 20 is heated above a particular temperature this condition may be referred to as a first state of operation of the actuator 10 thereafter when the retained part 30 has been inserted into the reception sleeve 40 and the capturing part 20 is cooled the internal diameter d 1 of the reception sleeve 40 may decrease slightly until an interference fit may be established between the reception sleeve 40 and the retained part 30 the establishment of the interference fit responsive.