Card Sleights - Double Undercut

I would like to start a few tutorials on how to perform some card sleights.
This is the first in this series and I hope it will be useful to beginners in card magic.

Double Undercut

Let us suppose that the top card is to be moved to the bottom of the deck. The right hand holds the deck from above (in the Biddle Grip/Count). A break is held beneath the top card with the right thumb. The left hand then cuts the bottom half of the deck off and places it on top of the top half. This is repeated, with all the cards beneath the break going on top. The deck has apparently been fairly cut twice, but in fact the only change is that the top card has been moved to the bottom.

Here is a variation of the undercut on how to cut the deck and bring the top card in its original place again: