I am not a person who believes that cats are better off indoors. The outdoor world has too many benefits to count, both for body and soul, for all living things on this planet.
Having said that, the world surrounding our homes is not safe for our pets to roam freely.
I looked into fencing my yard, but all the options seemed to focus on keeping the cats in, while what I needed most was to keep the wild creatures out. They were also prohibitively expensive for me.
Then I found this manual online (Just4Cats). It was perfect for me. The man who wrote it experimented for years before coming up with the plans for this enclosure.
The instructions are geared toward people with no building experience. The plans are modular, so you decide how large to make it, and in what configuration. It's mostly 2x4's and chicken wire, so it's not too expensive, and every detail, every nail and piece of string you will need, is laid out for you.
I am using a heavier wire on mine, using the guidance in the manual, since there are fisher cats and coyotes in the woods around my house.
I am not quite finished with it, but am far enough along to say with confidence that the plans are very easy to follow.

Pros: inexpensive, adaptable to your needs, easy to build

Cons: DIY

I think this is great idea my cats are always trying to get outside and noew they can safely. My cat have never been happier

Pros: cats get to go outside

Cons: none

I have built an outside cat play area to keep the cats safe. The manuel was very helpful.

Pros: good to know, info

Cons: none