Abstract: This invention relates to a pressure/vacuum system apparatus; one part of such apparatus being an economical fitting, another part being operating mechanism, another part being a means to join such fitting to such operating mechanism in a substantially fluid-tight manner, all operable to perform certain functions together without shutting down the pressure/vacuum system they are attached to. Some installations require many fittings. In many instances an operating mechanism may be attached to an operated fitting for only short periods of time and then disconnected therefrom, leaving the operated fitting in (a) a dormant condition in relation to its functions to the pressure/vacuum system, or (b) in a functional condition in relation to the pressure/vacuum system. Thus, in many cases a single operating mechanism may be used for operating each of a number of different fittings from time to time as required.