Pull the rope end downward and voila! It's a figure-of-eight knot!
This tutorial will show you how to make the extremely necessary figure-of-eight knot (aka. savoy knot, Flemish knot). The figure-of-eight knot is used when sailing and/or rock climbing. This knot is used as a method of stopping ropes from running out of retaining devices. Sailors knots in general are used because they can always be unknotted. You can pull on the sailors knots as hard as you like, but they will always be able to come apart, so you never have to cut the rope. This is of course extremely useful when sailing or rock climbing because you want to keep your ropes at the desired length.