a three - wedge double block isolation chamber including a body with an internal chamber bounded by an inlet and an outlet having a wedge assembly positioned in the chamber . the wedge assembly may be configured as either a blind wedge assembly to block the flow of liquid through a pipeline ; a flow - through wedge assembly to permit flow of liquid through a pipeline ; or a meter wedge assembly to meter the flow of liquid through the pipeline . the wedge assembly includes an upstream wedge , a downstream wedge , and a force wedge . the wedge assembly seats in the internal chamber of the body . the upstream wedge and the downstream wedge each include a seal and are positioned respectively against the inlet and outlet . the upstream wedge and the downstream wedge each also include a tapered surface to mate the tapered surface of a force wedge such that when the force wedge is inserted between the upstream wedge and the downstream wedge , a force is applied so as to seal the upstream wedge against the inlet and the downstream wedge against the outlet , thereby producing to independent seals , one on each end of the internal chamber of the body . when the blind wedge assembly is positioned in the chamber , it provides a double block and seal to assist in the prevention of flow of a liquid through a pipeline past the isolation chamber .