Can you give me a small example of how to do that?
Imagine you're a post-office worker, and part of your job is to delay the mail (I'm pretty sure the Royal Mail operates like this).
You've got a set of fifty pigeon holes.
A letter comes in, so you put it in the first pigeon hole, then a second, and so on.
When you've filled in fifty holes, it is time to send out the the first letter.
You don't take out the first letter, then go through each box, shifting the contents into the previous box, do you?
You take the letter out of the first box (the oldest one in your list), and put the most recent letter in its place.