About ten years ago, I went to my father's work one Saturday afternoon. He worked at [big software company]. Throughout the entire building there were doors tha

About ten years ago, I went to my father's work one Saturday afternoon. He worked at [big software company]. Throughout the entire building there were doors that were locked, and to open them, you'd put your badge next to the scanner and the door would open. These doors were everywhere. The doors had to be able to be opened from the other side without a badge, though. In case there was ever an emergency, people would need to be able to get out without a badge. I noticed this when we let the building for lunch: the door was automatically opened as we walked towards it. When we got back from lunch, being the curious ten year old I was, I tried to figure out how it worked. It turns out they had a motion detector pointing in front of the door, and whenever it detected motion, the magnetic locks on the door would open. So, I asked my father for a stack of paper, went to the elevator room on the locked side of one of these doors, and for thirty minutes made paper airplanes and threw them through the crack in the middle of the double doors until I found out how to make a plane which would expand enough to trip the motion detector. After another half hour of practice, it would only take one or two throws to trip the detector. The next time I visited his work, and after a few emails to the building security, the cracks in all the doors were sealed. I've been interested in security ever since then.