I recall one time, I listening to a friend trying to explain UNIX permissions to another friend of mine. They were not getting the concept. After about ten minutes of explanation, I interjected and the following dialogue occurred.
“Well, you see, it’s a series of three bits, you add up the numbers and then you end up with a three digit number that represents your permissions.”
“I’m not sure I get it.”
“IT’S FOUR PLUS TWO PLUS ONE IS SEVEN! IT’S NOT ROCKET SCIENCE!”
This is why I’m not in the training department.