How to turn on & use it:

1. Rotate the locking screw clockwise to tighten the device or rotate counterclockwise to loosen the arms so they can rotate.

2. Inside corner: Fold both arms together and place the tool firmly against the surface. Press ZERO button to calibrate. Open one arm —the display will show the measured internal angle.

3. Outside Corner: Open both arms flat and place the base of the tool firmly against the surface. Press ZERO button to calibrate. Close one arm — the display will show the measured external angle. This mode also allows measuring angles from the x-axis as is typically done in mathematics.