looking for 2 box schematics

[TheGreenBoy]

Anyone with good two box schematics? I need to find void / tunnel in rocky soil (rocks predominantly).
Thank you.

 

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[Melbeta]

To tell you the truth, I used to be a metal detector dealer, and I sold 2 box units. I do not believe they will find a void. They only find metal and find it fairly deep. What are you looking for? If it is a cave, and you are fairly close, I would make a rod probe, and probe the area. Maybe I can tell you something that you can use.
Melbeta

 

[TheGreenBoy]

Thank you.