Yes, Thanks sunnychooks. We do have hardware cloth about 6 inches down, but it just stops there. Before we got the chickens, we had never seen a rat, so we thought that even the little rodent proofing that we did was overkill. Now we know better!!
On a positive note: the rat zapper works...
The sharp edges are what I was concerned about. But, I think if I staple the hardware cloth low enough on the 2x4, I can back-fill with enough soil/sand/gravel that is should cover it. Since I am planning on loads of work anyway, I may take the time to fold the sharp edges down when I staple...
I am fighting the rat battle. I bought a rat zapper, but nothing yet. I have only had it two days, so I'll give it time. But, I am wondering if this idea would work:
Dig about 1.5 ft down in run, place hardware cloth, stapled to 2x4's at ground level of run, replace soil/sand/pea gravel over...