detail wherein like numerals designate like parts and referring first to fig1 a prior art receiver frame 10 of the type shown in u s pat no 4 329 005 is illustrated the receiver frame 10 includes spaced opposing parallel side members 11 and 12 having aligned notches 13 formed therein to receive multi contact module bars 14 these prior art module bars have their opposite end portions engaged in the notches 13 and are retained in the frame 10 by front retainer strips 15 which extend entirely along the side members 11 and are attached thereto by screws 16 which can number as many as twelve or sixteen per retainer strip 15 the retainer strips 15 overlap the ends of the module bars 14 and hold them securely in place in the receiver frame 10 the sides of the module bars 14 away from the strips 15 rest solidly on rear fixed retainer elements which are not removable as stated previously the main feature of the present invention is the elimination of the front retainer strips 15 and the large number of screws 16 securing the strips to a receiver frame or the like in accordance with the invention multi contact module bars 17 are equipped at their opposite ends with longitudinal axis cylindrical snap locking plungers 18 having narrow beveled faces 19 adjacent to their rear sides with relation to the adjacent receiver frame member 20 this frame member 20 fig2 forms part of a rectangular receiver frame or in some cases an individual test adapter frame having an opposite side member 21 and a pair of end frame members 22 as.