Port knocking. For example, you configure your router to covertly be watching a set of ports. Let's make it 1337 followed by 51115. It is programmatically configured to, upon receipt of packets on each of those ports, open a remote login capability (be it remote desktop or sshd or whathaveyou) on port 6337. This is an example of security by obscurity. Your network is not inaccessible just accessible by an attacker looking for this rather arbitrary protection. If the protection is public, it is useless.
An example of a false security can be buying an expensive car with security features which at the end you think can protect you if you drive recklessly. This is too insignificance with how the car is supposed to function and how the features are supposed to help you.