That's what I've always used..

as long as the nail is long enough to get really set into the mortar and that you don't break the mortar setting the nail.. I think they make those with screws, as well.. you could drill a smaller pilot hole in the mortar and then screw it down tight..

I dunno that they make any kind of expandable screw that small, but that's the way to go.. I just drilled new holes and used expanding bolts to tighten down the iron fence to our courtyard.. its solid as a rock, now..

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