To turn the unit on and off, you'll need to hold the righthand button. There are no labels on the front of the unit, so you have no choice but to read the instruction sheet to learn how to use the RAD-1. You'll also have to remember that the side-to-side (pitch) angles are on the lefthand digital numbers, and the front-to-back (roll) angles are given on the righthand. The RAD-1 comes preset from the factory with a 0-degree setting for both the X and Y axes. When putting the RAD-1 in your vehicle, it's a good idea to use a good, old-fashioned bubble level to make sure that the vehicle is on a level surface.