joining rocks with rods... what type is good?

[Chin_Lee]

Thanks Nate. Interesting idea with the sand sectioned off.
I thought about using 1/2 sch40 piping but I would need to buy at least a 5/8 masonry drill bit to fit that into the hole. Since I'm probably going to throw away the very rust masonry drill bit later, I'm tempted to go smaller (the bits gets much more expensive as you get beyond 1/2").
What I want to do is build some arches and I would like to support the bonding of the rocks with zap straps and rods and then maybe epoxy the joint slightly to make it look smoother. But I'm just not sure what material rods I should use.