I agree Jubillee, I have no idea why a gag is called a gag, but it makes it sound in my opinion more horrible then what it really is. (and just to note, it does NOT function by 'gagging' the horse) . There are several different types of gags differing in severity and function. Generally you'll have 1 main rein that you ride off of, and a 2nd gag rein that you use when you need extra leverage, very much like a pelham. I would disagree with the 'ehow.com' article someone posted that it's 'the most dangerous of all bits'. I think a double bridle in the wrong hands can do more damage (and really, a snaffle in the wrong hands can do damage). But like how a double bridle can give an experienced dressage rider the extra precision and control necessary to do upper level movements, a gag can give a jumper the extra precision and control necessary to the jumps, esp on a horse that's ready to GO and may be too excited to listen to the softness of something like a snaffle. My barely 5'2 petite frame does not have the leverage a 6 ft man will have on a huge fit jumper no matter how well trained that horse may be. I start every horse in a snaffle and ideally, it'd be nice if every horse could go in one, but that's simply not the case. But there's no point in over bitting your horse either as you don't get the best results doing that. That being said, for a rider to properly use a gag, because it can be strong, it is absolutely crucial that you be able to balance/jump without needing your arms, have a very soft hand, and ride mostly off your legs/seat. It's not a bit for everyone and I wouldn't recommend it to most people but certain horses do very well in it, which is why it's somewhat common in the jumper ring.