slots 41 provided in the inner housing 15 as illustrated in fig4 a hydraulic mechanism not illustrated is provided in association with the opposite end of the engaging bar 42 to selectively apply pressure on the engaging bar 42 and force the operating end of the engaging bar 42 into the brake slot 41 in the inner housing 15 against the bias of the bellville washers 44 to prevent rotation of the inner housing 15 and the stripper rubber 20 within the outer housing 2 upon release of hydraulic pressure from the engaging bar 42 the bellville washers 44 assume their original configuration and force the engaging bar 42 outwardly thereby disengaging the operating end of the engaging bar 42 from one of the brake slots 41 provided in the inner housing 15 and allowing the drilling string inner housing 15 and the stripper rubber 20 to again rotate with respect to the outer housing 2 in operation the rotating blowout preventor 1 of this invention is typically used in association with one or more additional blowout preventors to seal a well during a drilling operation as follows the rotating blowout preventor 1 receives a drill pipe 50 of a drilling string which extends through the stripper rubber 20 of the rotating blowout preventor 1.