The crest release is the most popular use of the hands for jumping in hunter classes today but it's sort of usurped the position of the automatic release.
A quick description: crest release is when you lean your hands into the crest over fences. There is a short release and a long release. The purpose is to release all contact with your horse's mouth and keep him from getting his mouth punished over jumps. It was originally intended for beginners. The automatic release is when the hands follow the mouth over the jump maintaining contact and not leaning on the horse at all. There should be a straight line from the mouth to the hands to the elbows.
Some people believe George Morris was the innovator of the crest release but he wasn't. He only gave it a name. It was first taught by Littauer in the 30s. He used it as a quick way to get students jumping because he said they couldn't get fit and strong enough to jump without leaning on their horses. Then Gordon Wright (George Morris' teacher) continued the idea during the 50s and then G. Morris went on with it.
The crest release is intended for beginners. Before G. Morris began pushing it you wouldn't have considered going into a Medal or McClay class if you had to lean on the horse to jump. G.Morris actually teaches that you should support your upper body with your hands, making it part of the base of support. Even so, riders put more and more of their upper body weight into their hands, on their wrists, on their arms, to the point that they are laying on the horse. Then it becomes dangerous because it takes the weight out of your heel and leg where it should be and makes the rider vunerable if the horse stops or has a bad fence.
The crest release also encourages getting ahead when you jump. Getting ahead not only makes the rider unstable, it throws the rider's weight on the horse's forehand making it harder for him to jump.
But there are more problems. Too many use the release incorrectly and you see horses jumping in tight reins. The crest release is supposed to release contact with the horse's mouth. The crest release also creates horses who need stronger bits because they are either jumping in tight reins (bad crest release) or loose reins which means the rider loses a little control of the horse, so riders use stronger bits and more gadgets. The automatic release gives the rider smoother, lighter control.
And lastly, people are beginning to forget what an automatic release is and don't want to progress past the beginner crest release. People are jumping higher and higher with crest release and the horses are the ones paying the price for it.
If an eventer uses a crest release for anything except an emergency, they're inviting a serious accident at some point. I'd love to see everyone progress in their riding so they can use the automatic release naturally and save the crest release for when they have a sticky situation or a very unpredictable green horse they want to be sure not to hit in the mouth or back.
Keep up the good work. Explaining the releases and why you use them and like/dislike them helps everyone