We have tenants that have carved holes on the drywall to access the heat pipes and AC mains. At some point they will patch the drywall very well. Perhaps by another piece of drywall that closely fits the hole and all that had to be done is paint it over and it will be as if nothing had been tampered.
So I need a way to detect any discontinuity on the drywall piece (sort of like a stud finder) if such a technique exists.
Of course, I can simply find where the AC mains and heat pipes run through and then sand the wall right in front of them and viola, I've found the patch. But, I was wondering if such a technique exists.