Gate post fixings to stone wall

[lanham]

My son needs to attach 10cm posts to a wall. His problem is that the wall is sandstone and he is afraid that something like 'Hammer Fixings' or 'Concrete Bolts' might not hold firmly. If he uses either of these fixings, what sort of length would he need? Unless there is a better way of doing it of course.
Any help would be appreciated.

Thanks

Brian

 

[Wayners]

Chemical fixing. Resin.
Threaded bar
Drill
Fill with resin
Push bar in and wait a few hours to set
Washer and nut to hold wood