Fitting headlamp grilles

I've been fitting a few bits and pieces on my girlfriend's Defender. We got some hinged headlamp protection grilles from Paddock's, but I can't quite work out what some of the bits are for. With each pair there is a hex bolt and a black bar with a hole in it, and a little diagram which leaves me none the wiser. Before I go drilling holes I would like to know exactly what size and where. All bits shown in the attached photo.
Cheers

The bar is for "setting" the riv nuts. Once they are fitted you dont need it any more.

Thanks; I just had a similar reply in another forum, complete with photos for idiots. It seems rather obvious now!!