Limit of Positive Stability or LPS is the angle from the vertical at which a boat will no longer stay upright but will capsize, becoming inverted, or turtled. It is also known as the Angle of Vanishing Stability or AVS. For example, if a boat with an LPS of 120 degrees rolls past this point, i.e. its mast is already at an angle of 30 degrees below the water, it will continue to roll and be completely upside down in the water. Most sailboats have lead or other heavy materials in their keel at the bottom of their hulls to keep them from capsizing.