"S" Bit- Explained?

Maybe I should have explained this a little further. Believe me my horse tries to crib on the bit, weather you believe it or not. My instructor Mari Monda Zudunic said to look into an S Bit, shaped like a letter "S". I now use a Mullen mouth bit which my horse likes, he is just so busy trying to grip on to the darn thing he doesn't even watch where he is going or what he is doing. My horse isn't your typical cribber, he doesn't latch onto stuff and pull down sucking air. He grips onto anything metal and sucks, (like a pacifier) it is pretty strange. Teeth have been done, and he is a happy well behaved horse other wise. I will also try the bit guards, I have them and it is worth a shot.