Just DIY. We are lucky in that the yard already has walls on four sides (house, high yard wall, shed/garage front, low yard wall) and is only around 12 ft x 12 ft. Not sure how much use my method will be to a non-terrace type garden.
Cat-proofing was basically to stop our cat jumping up over the low wall (she used to be able to tackle the others, but got too old) and to prevent other cats jumping in. So what we did was:
- Build the low wall up to about 8ft height with trellis (with gaps smaller than a cat :-) and metal mesh to match height of the high wall and shed.
- Stretched some bungee cord from shed to house along either side, to support some green garden mesh stuff which was secured with loads of cable ties.That blocks the 'jump down' routes for outside cats, and any escape attempts from inside too. There's a gap in the middle but it's too big a jump down for any cat so far to try, no easy landing points. The bungee elastic keeps the cords in tension and gives them a pleasing curve :-)
So far it's worked well - been up well over a year (or is it two?) and also survived plenty of snow over the winter - the mesh sags a bit under the weight of snow but isn't damaged.
Not easy to get a good pic but this gives an idea:
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