To mount antennae along the top edge of the guard(s) you'll need a appropriately shaped bracket.
These come in various profiles to suit the inner edge of the guard and how it mounts. Downside is that the guard to bonnet gap on some cars is fairly small and that makes both bracket mounting and feeding the cable through difficult.
Examples might look like this:
Screenshot at 2022-05-18 16-08-44.png
Your other option would be to mount at the front of the bonnet with the bracket mounting on the top of the radiator support panel and poking out under the front lip of the bonnet. This makes cable routing much easier.
Screenshot at 2022-05-18 16-09-17.png
You'll have to do some Google searching to find the shape you need (above pics came from telcoantennas.com.au) and sometimes it is necessary to modify the angles/folds, which is easy enough to do in a vice.
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