This device allows you to measure the relative angle between two surfaces, making it ideal for setting the pitch angle on ground-adjustable propellers. First, you set the angle on the first blade. Then you can set the other blades the same or zero the display and set the second and third blades to zero.

The display always reads left to right, even if inverted, and a “hold” button keeps the measurement for reference. It has a range of 90° left or right and a resolution of 0.05°. The unit is approximately 2-¼” square by 1-¼” thick, has an easily readable liquid crystal display, and can read absolute angles for measuring level and plumb or can be zeroed to set repeat angles.

Rare earth magnets on either side and on the bottom hold it securely to any ferrous surface. Two small rare-earth magnets available from Princess Auto placed on the opposite side of my Powerfin prop hold it in place. The device is available from Lee Valley for $24.95 until April 28. After that, the price is $34.95.