Last night as I was teaching my AOH Group, one of my students wanted to tell a “funny” story.  As I teach people I find that their hand position can go from good to bad through neglect.  My suggestion was for them to buy a small mirror like a makeup mirror that they can put in front of them when they practice their practice chanter.  With the mirror, they can see and adjust their hand position.
One of my students actually took my advice and bought a mirror.  He was practicing with the mirror on his coffee table while he sat on the couch.  When he was finished practicing, he left the mirror in place.  Upon his return,  he found that there was a black singe mark on his couch that had burned into the foam padding under neath.  It turned out that the mirror had been left in the 5X magnification side and received some direct sunlight through his bay window behind the couch.
At this point, I am going to offer the same recommendation if you have a problem with your hand position, however I am going to advise you to use it at your own risk and release myself from any liability in the use of the mirror.  Thank God that was all the damage, it could have been a lot worse! 🙂