I was sitting on the throne one morning with the door closed, maybe an 1/8 inch space under and I watched a mice crawl under, it saw me and it let out a squeak and slid under the sink vanity with about an 1/8 inch space. They don't need much room at all the squeeze through. It did all this with a piece of cat food in its mouth. When we replaced the vanity a couple years ago there was a pile of cat food in the corner.