The lark’s head is an enormously useful knot and quick to make once you’ve mastered the thumb and finger pinch action. It’s great to use when you have an intact circle with no ends available, such as a rubber band, or when you have a loop. It also can be made with a length of string folded in half (with two tails). It’s used to attach things—what is to be attached is encircled and held secure in the knot’s loop, which draws up and holds the object tightly. It is extremely secure and can’t come undone.