Predator-proofing: our net design

We love our quail! We are also pretty happy with our net, despite occasional incursions by rats and persistent attempts to get in by currawongs...
It's a big area - 30m by 50m -  and we needed enough height to fit our fruit trees inside, without possums being able to jump on the net and reach the leaves.

The net - looking in from outside

 We bought 16 treated-pine poles, 4m long, and put them in holes around .5m deep. The soil is really easy to dig, and we didn't cement the poles in, allowing them to shift a bit with the wind. We drilled holes in the top of each pole and threaded high-tensile wires through, attaching these to the ground with metal stakes (hammered in to a depth of at least 1m.) The wires are held as tight as possible, to keep the net taut.

Pole and holding wires - each pole is anchored to the ground in three places

 We put 'tensioners' on each wire so we can crank them up really tight, and re-adjust if needed. This has been really useful after high winds, when the poles shift a bit. Not having them on a concrete base means they are much more flexible - I am pretty sure they would have broken by now if they'd been held fast.

Wire tensioner

 We then covered the poles and wire framework with strong black nylon bird netting (commercial grade). Getting the net over the wires was by far the hardest thing to do - it came in huge bags, 100m x 10m, and 100m x 5m. We have quite a lot left! We pulled three rows of 10m net over the top, and used the 5m width for the sides. We clipped the pieces together with plastic clips provided by the netting company, but we didn't tie it well enough and butcher birds got in through the joins, killing two of our quail. We then stitched all the joins together with wire - this took the best part of a week, standing on a ladder, doing a metre or so at a time.
The final bit was adding a strip of chicken wire along the base. This we dug into the ground so rats couldn't burrow under it, and stitched it to the nylon netting at the top. We thought that was pretty good, until we realized rats could get through the chicken wire and bite through the nylon netting...we had to add a second strip of smaller-gauge chicken wire, and fasten that tightly to the first piece, and to the netting, to make a thick wire layer rats couldn't wriggle through. It works, most of the time. Every so often we find a hole eaten through the black nylon netting and we know a rat has got in...we patch the hole, and set traps until we catch the rat.

Patched nylon netting where a rat has got through

No possums or wallabies or large birds have got in, and the quails - and the fruit trees - are thriving. It's held up in winds of more than 100km/hr, as well as being covered with snow (albeit lightly). It's not 100% rat-proof, but it's the best we can do!
We'd love to hear how other people keep free-ranging quail protected!