I jammed with a few guitar players and drummer friend a few weeks ago. One of the guys, who I had never played with before, was a fairly decent player but did not know where the notes where on the fret board. When I tried to give the notes of a signature guitar riff on a song we were about to do, he got all indignant. Turns out he did not know where the notes were and I had to show him fret by fret to teach him. This probably took five minutes. Question is if I give him this teaching aid shown below as a gift, would that be interrupted as an insult. He is a friend of a friend and I don't want to stir things up. With that said, chances are I will never play with him again. What do you think?