In pre-cable days, you would have a TV antenna on your roof. It would have a little motor that would rotate the shaft it was mounted on so you could "aim" it to give you the best TV signal. This was the controller for the antenna on your roof, and it would sit on your television set.
I put aim in quotes because the aiming was not very precise. You'd find what works best for a particular station and as other have alluded to, mark that on the controller so when you put Channel 4 on, you'd rotate the antenna to the spot that usually works best for Channel 4. But depending on the weather that might not even give you the best reception for that channel.