Andrew showed John the spell to reveal flaws in the net and showed him how to either spread the beam of the spell out to cover a bigger area or how to concentrate it to perhaps look deeper at a suspected flaw in the protection net. He showed him what the net normally looked like when it was revealed--like a white sparkling haze that covered the air over the property. And a flaw generally looked like a hole in the net. At the edges of the property, the net needed to completely touch the ground. Things like doors, holes, caves, etc, needed to have extra coverage because they could be vortexes for penetration.
"So far, the net looks strong," Andrew said. "And any other color above the net is a spell trying to get in. Other colors inside the net are spells that have already gotten in. And, well, a hole is a hole, no matter how you cut it. John, you can't tell anybody you know this spell. Its an advanced spell for NEWTS. But you hang out around Robert long enough and, well, he sort of rubs off. Hanging around Brian gets you the same thing. Its not bad, but you do have to keep your mouth shut about it."