We have a regular door lock, a deadbolt, and a hotel style non-locking hasp that is too high for them to reach even on a chair. If they get through the door, they then have to figure out how to unlock the storm door. If they were to escape out the patio they wouldn't be able to scale the 6' fence or open the gates because the lock is on the outside. Pretty sure at least one of our dogs would be going out with them, so they wouldn't freeze to death either. I think our set up is pretty damn secure, but we made the effort to get it that way.