[RosieCotton]

I wonder if it would be worth it to look into one of those pet doors that only works if a dog has a key thing on its collar? That would mean if I didn't put on on the cats, they couldn't get out, right?

They're expensive, though.

[HairOfTheDog]

They might be a little more expensive, but less expensive than the covered run! If you had the triggered door (and they work perfectly!) you could put in a much cheaper fence.

[HairOfTheDog]

For little dogs, Home Depot sells ready-made picket fence sections, for example... less then $20 per 8 foot section. A friend with a little dog did that... and it looks really nice. Would keep a doxie in. (I have seen a type of picket/mesh combo that you buy on a roll too)