When I first started coaching ten years ago, I had no rule book but I knew the rules
Unfortunately, a few things had changed since HS. I was all over a ref for a 5 second count because my guard had penetrated past the hash mark - "hey, you can't call 5 seconds!" Unfortunately, that was true in 1978 but not in 1993.
Luckily, one of the refs was "experienced" enough to know the old rule, and asked me when I last played. He then suggested I pick up a rule book, cause things had changed quite a bit since then. One of the many good things I have done as a coach.