video: https://www.instagram.com/reel/CO6Ck6dJIvn/

Try googling catios.

I just want to say how wonderful of you to think of otherwise homeless cats! I wish you the best going forward.

I don't think the cat shelter shown in your photo is an ideal structure for your cats. They not going to be comfortable in a catio that is so enclosed along the ground and the only area they can see out are the high windows.

Do you have any problems with predators, how extreme is your weather and do you intend to keep them in the enclosure full time? Keep these questions in mind when building a structure.

If you intend to keep them in the catio make sure all the cats get along and the enclosure is large enough for the number of cats you have.

Also, if you're going out of town, be sure someone else is caring for them if they're enclosed (or not). Things happen on trips and you'd hate to be delayed somewhere and the cats left without someone checking on them.

As you'll see in the link below, catios can be built from a variety of materials. I used a large dog kennel for my indoor/outdoor cat but it attaches to our basement so she has shelter indoors when we close her in at night. I covered the top with lumber and chicken wire to keep out predators but it also keeps her from climbing out.

These sites should be of help.