Use this tool to easily align your solar panels with the sun. First find true south (northern hemisphere), or true north (southern hemisphere). Face the panels for your respective direction. Use some double sided tape to temporarily mount the tool to the top corner of your panel. Adjust the angle of your panel till the shadow is in the horizontal channel. When aligned correctly, the shadow will move from one side to the other along the horizontal channel as the sun moves in the sky. At high noon, the there should be no shadow. 

Works best in a light colored filament. Black filament not recommended since it'll make it harder to see the shadow.