I used 1/4" hardware cloth for the bottom 36" and uncoated 1/2" HW cloth for the upper sides of my run. Because dogs could eventually tear through the 1/4" HWC, I put a layer of 24" welded wire rabbit fencing over the bottom two feet to make the tearing process much more difficult. The rabbit fencing is relatively cheap and gave the extra strength I was looking for to supplement the smaller gage HWC. My HWC is on the outside of 2x4 studs. If I wanted more separation for my birds from the outside mesh, I can put 24" chicken wire around the inside of the studs to keep my birds from being within easy reach of anything that managed to breach my HWC. I would put the Chicken wire up a couple of inches from the bottom footer, though, so that any debris that got between the layers of wire could be blown or swept out. I put part of my welded wire about two inches out from th HWC because it seems to signal my dogs that the birds are out of reach and should not be bothered.