Mothers....do you just open the door if someone knocks on it?

We have metal security screens on the front door. I can open the regular door, and still be behind a pretty strong door that you can't just kick through. Before we had those doors installed, I had one of those security bars, like they have in hotels, but metal, not a chain. So the door could be opened a few inches, but it would take a lot of force to open it all the way. It was also a very useful for keeping the kids in the house, because the bar was high on the door.