longitudinally of the channel the contacts 67 with their associated wires 13 may be inserted into the modules either before or after the modules are positioned in the channel 11 the end blocks 12 are of the same width as the modules 10 and given wall configurations similar to those of the modules including shoulders 103 which are engaged by the ends 98 of the retainer clips 95 to hold the end blocks within the channel 11 beveled corners 104 on the end blocks 12 receive portions of the beads 101 and 102 of the channel sidewalls see fig8 each end block 12 also has an opening 105 through it which is aligned with one of the openings 87 in the channel 11 when the end blocks is in place this provides an opening through either end of the connector assembly to receive a mounting screw or bolt used in securing the connector assembly to a supporting structure by providing openings 87 throughout the length of the channel 11 there will always be an opening 87 aligned with the opening 105 in each end block 12 irrespective of the length to which the channel is cut for accommodating a given number of modules 10 the modules may be removed from the channel 11 by means of a tool 106.