Abstract: An actuating mechanism for moving an indicator, an operational tool or a structual component with a high degree of precision over precisely predeterminable distances to desired points of operation, which comprise a shaft, slidably mounted upon said shaft in end to end relation a sequence of interconnected actuating components of selectively variable length axially of said shaft each having limit stop means for positively and precisely predetermining its conditions of minimum and maximum length and thus its possible increment in length, said increments being arranged to differ for the individual components, means at one end of the sequence of components on said shaft for positively blocking movement of said sequence of components in one direction while leaving the opposite end free to move on said shaft in response to increases in the axial length of any one of said components, means selectively operable to actuate said components individually so that they assume either their condition of minimum length or the