Have you ever seen a really old door on a house or stone wall with the thick iron hardware that creeks every time it opens? Back in the day, big heavy doors stood as formidable barriers that couldn’t be breached by force. Yet many of these doors were no match for prying eyes. The huge iron keys required to unlock the latches were so wide that you could actually put your eye up to the keyhole and look through to the other side. Nowadays we have small metal slits for slender keys, and sometimes only touch pads, so we can’t peer through keyholes to catch a glimpse of something beyond.…