Abstract: A holding fixture for use in the brazing of heat exchangers applying multiple holding pressures, two of which are in senses opposed to one another. Cage members mount a heat exchanger between them and are biased in a separating sense. At the same time they incorporate apparatus to apply a clamping pressure essentially within respective cage members. Fixture mechanism includes a detachable part useful as a reactant member in application of the clamping pressure and as a dynamic retainer in applying a pressure in conjunction with a separating motion of the cage members. The invention has method aspects related to brazing in the presence of multiple applied pressures.