This is the simplist knot of all. It is commonly use to temporarily "stop" the end of a fraying rope.  The
overhand knot is commonly tied in a eight formed at the end of a rope, forming the Overhand Loop.  This knot is also known as a Thumb knot.

Tip. The Overhand knot jams easily so it is far better to use a Figure of Eight knot to stop fraying.