Instruction manuals for all your electronics, collars, GPS devices, etc. I know, I know, we should all be familiar enough with our dog electronics that we don't need to consult the manual, for anything. But are we? I'm certainly not. I have a well-deserved reputation among my friends for technical incompetence, and last year on a hunt in Kansas one of my collars kept losing synch with the transmitter. It was a fairly new-to-me collar, and if I hadn't had the manual to remind me of the synch procedure I might still be out there scratching my head.