Braiding adds polish to a jumper's turnout. A loose mane can look messy at times but a neatly braided mane will help make any horse look great. One of the great things about braiding in the jumper ring is that the style doesn't matter! Most braiders will use button braids for jumpers. These are the same type of big, round braids that is seen on many dressage horses. Button braids use larger sections of mane and are therefore fewer in number along the neck than is seen with hunter braids. The exact number will depend on the horse's mane and your preference for looks and braiding time! Other types of braids that are seen in the jumper ring, albeit less often than button braids, are hunter braids and running braids.
The forelock does not have to be braided for the jumper ring. If you do not wish to braid it, the forelock can be left loose or it can instead be covered with a quality fly veil.
Some classes that are run in the jumper ring do expect braided horses. These are jumper equitation or medal classes. Horses can be braided with either hunter braids or jumper braids for such classes, although hunter braids are generally considered to be more acceptable for more formal classes.
For a tutorial on one method of braiding a jumper with yarn, see Foolproof Jumper Braids.