Designed by Art Lebedev, the Defendius is supposed to protect unauthorized entry through a door. However, honestly, I don’t see how this helps burglars from entering through your front door. I mean, mechanically, it’s like any other door chain, except the Defendius is a pain in the ass to open. To open the door, you have to go through a maze. In fact, it probably makes it more tough for you to get outside, than for a crook to get inside.