Here's a versatile 3-piece set of mirrors that you can tape together, fold up, and insert into a soundhole.
When unfolded inside the guitar, it gives you a 7-1/2" x 12" flat viewing surface, for the big picture of the guitar's interior. Made of nonbreakable mirrored acrylic, it frees both your hands for the job. Supplied untaped.
CALIFORNIA PROPOSITION 65 WARNING