When @dragonjaze got home she wanted to see how Cosmo fit through the hole, so she took out the bricks and waited ...

http://www.youtube.com/watch?v=4quC_LUNliM

You can see our terrier mix poke his head through, which is all that fit. He was thoroughly upset about that. Kota throws tantrums if he's separated from his mommy and brother if he knows they're together.

Also, @dragonjaze pointed out that the hole was always there, but there was always a big bush directly behind it which she just took out this past weekend. A couple minutes with stakes and fencing, same as she has put up around the flower beds, and it's fixed.