Joe sent in this is a really beautiful way of securing a door. The design was inspired from magnetic core memory that was used in early computers. In this case, the final product is used for keeping a dog from breaking the glass while trying to attack the mailman! [Thanks Joe!] Magnetic Core inspired Door grill
Before there were hard drives–before there was RAM (random access memory)–there was magnetic core memory: An arrangement of donut-shaped magnets, the polarity of each could be switched by the current of 2 wires passing through the hole. In this way each magnet could be set to an “on” or “off” (binary) position. Needless to say, they don’t make memory like that anymore.
And here is the inspiration for the door:
More about making a Magnetic Core inspired Door grill