transversely into alignment for their nesting engagement as the connectors move longitudinally towards each other thus each opposed pair of connectors 42 and 42v is self aligning independently of the associated pair of horizontal and vertical circuit boards 18 and 20 fig6 shows one of a plurality of flat head screws 82 used to mount separator 36 against circuit board 18 each of wires 73 includes a 90 u00b0 bend and extends downwardly to a connection into circuit board 18 a spring metal ground connection 84 is fastened to separator 36 by screws 82 and runs substantially the length of the separator a portion of ground connection 84 extends outwardly beneath and against legs 40 and connectors 42 and is used in connection with the back plane grid to provide a ground for selected circuits as is later explained also seen in fig6 is a relatively steep bevel 86 provided at the outer end of each chamfered edge 78 bevels 86 provide an initial aligning between connector 42 and grid 88 when circuit board 18 is inserted into position before any of circuit boards 20 are in position similar bevels 87 are at the ends of chamfered edges 80 fig7 shows part of a row of connectors 42 supported in a portion of separator 36 and facing a back plane grid 88 preferably machined from a single piece of aluminum for optimal grounding capability only part of grid 88 is shown and outer frame portion 22 has been removed to enhance illustration of the grid in use the grid is positioned between the opposed stacks of vertical and horizontal circuits boards with vertical rows of contacts 42v facing grid.