Abstract: This specification is directed to a rack assembly (40) used in the vacuum brazing of aluminum heat exchangers (10). The rack assembly of this invention includes an upper rack support structure (42) having front (44) and rear (46) facing portions. A pair of rails (48--48) are mounted from the upper rack support structure so that the pair of rails extend from the front facing portion to the rear facing portion thereof in a spaced-apart relationship. The spacing (50) between the pair of rails is sufficient that fluid tubes and fin strips of a heat exchanger can pass therethrough while an upper header member thereof is supported on opposite sides of the pair of rails. An upper locking structure holding device (52) is mounted on the rear facing portion of the pair of rails for holding a locking structure (66) therein. A releasable locating structure holding device (54) is mounted on the front facing portion of the pair of rails for releasably holding a locating structure therein (78).