this rotationally locks ramping washer 17 to the base plug 12 in fig3 ramping washer 16 is shown with three annular ramp faces 16a 16b and 16c which match ramps 17a 17b and 17c when ramping washers 16 and 17 are emplaced ramp face to ramp face as indicated on fig2 thus rotation of one ramping washer with respect to the other is translated into axial motion i e the effective thickness of the ramping washer pair is a function of their rotational relationship it will be particularly noted that with the multiple ramp configurations of fig3 and 4 the axial forces generated are uniformly distributed circumferentially this would not be the case with a single slope ramp surface such a uniform locking force distribution is particularly advantageous in the spacecraft application aforementioned the spacecraft skin surfaces to which the locking forces are ultimately applied are normally coated with glass like protective coatings which are subject to cracking and crazing particularly if heavily paint loaded the silicide coating applied to columbium base material hereinbefore mentioned is such a glass like material it will be realized that either one of the ramping washers could provide the base plug stem locking feature i e either one could have shape 17f but of course not both the one not having this shape being the rotationally positionable one such as indicated for ramping washer 16 in fig3 in fig1 and 2 a central bore in 14 at 14d along with orifice 12c in base plug 12 provide a pressure sensing orifice particularly useful for the spacecraft application of the invention however the.