Basements and crawl spaces under houses make idea dens for urban critters. If we could charge rent for all the skunks, raccoons and feral cats that have taken up residence under the house we’d have paid off the mortgage by now. Our particular crawl space critter B&B was opened by virtue of a flimsy access door. Some animal, most likely a raccoon, pried it open. The problem with this situation is that you can’t just close up the door. Some poor creature would die a horrible death and then stink up the house for months. The answer is to create a one-way critter exit.