Where can I find the mouse holes?

Yes, it's in the wall decal section. It's kind of hard to spot. So I recommend filtering for the Cats and Dogs pack in the decor section.

I don't have Cats & Dogs, yet. I made a sim of my "evil" sis in law, wanted to put a mouse hole in her place.

The placeable mouse holes came with Cats & Dogs. The holes that came with City Living are not placeable unless you use a mod. Using the mod, you can place the holes and then remove the mod afterwards (if you wish.) http://modthesims.info/download.php?t=588505

I really like the idea of the a mouse hole.

Thanks everyone, I now have Cats & Dogs and have put mousehole in evil sis in law's apartment. Now I can do my evil laugh.

Do the decals function like the CL ones do?