I recently put up a couple of standard 2m fence panels; they stand at
the edge of a reasonably substantial drop though, so it's really
important they don't get pushed over (TBH I think I now regret not
having erected steel railings instead).

I've decided that it wouldn't be a bad idea to attach a length of mild
steel to the reverse (hidden) side of the fence, just below the top; ie
screw a 4m length to the three fence posts, so it would act as a rail
and prevent the fence panel from breaking and falling over the edge if
someone fell really heavily against it.

Question - what would be best to use: angle iron or solid steel bar of
comparable substance/cost - eg, say 20x20x3mm angle iron vs 12mm solid
bar? (I favour the angle iron in the sense it will be easier to get
through with my hand drill!)

Also - where, as a civilian, am I best going to buy this sort of stuff?
I don't normally 'do' metal; the last time I bought some steel years
ago I went to a local steel stockholder and got royally ripped off I
reckon...

--
David