Take two tennis balls and tape them together firmly.
Place them on the floor and then lie onto the balls, positioning them either side of your spine in your lower back.
With your hips raised off the floor, use your feel to roll your body and and down over the balls.
When you feel a tight, tender spot, hold this position until you feel the pressure release.
You can also use one ball to do this exercise on one side of your lower back, allowing you to move the ball to other areas.