One of the outermost layers is the screen lock pattern (or pin). With this pattern, you can set up a fairly strong bit of security that can prevent unwanted users from gaining access to your data.

Even in its default 3 x 3 grid state, pattern unlock is still a relatively secure solution. Admittedly, it's not quite at the level of a PIN setup, and there's a body of literature to back this ...

An on-screen pattern of light and dark gray bars used to balance the gray scale of a monitor. The patterns differ, but the goal is to obtain the optimum black. When on screen, the black level is ...