If you mean clipping as we would call shaving on humans, then it is really up to the individual, not all horses are clipped. but if they are clipped, and you want them to stay that way, just clip them when their fur is longer than you want.
A horse with a trace clip is where the horses back and legs are not touch and are left normal
Ouch!
Horses are generally clipped when they are in hard work during the winter and really sweating, though it's not necessary. Clipping is rarely NECESSARY, though many owners of horses with cushings disease will clip their horses for their comfort in the summer months.
Horses "clip clop" as the walk
It is called a bridle path.
When you clip or shave the section of mane behind the horses ear, it is called the bridle path. It is on www.Howrse.com riding level 2.
You body clip a horse using heavy duty animal clippers such as Oster A5's. There are different blade sizes for different parts of the horse or whether you want a close clip or a longer clip. You usually use a 10 blade on the body and a finer blade on the face and head. Bathe your horse to remove all dirt on the coat. A dirty coat dulls your clipper blades and can leave clipper marks on your horses coat that remains after the clip. You can begin clipping wherever you would like on the horses body. Going against the hair clip it off in short sections to avoid overheating the blade and burning your horses skin. Clean the blade often with a lubricant that cleans and cools the blade. If the blade starts to get dull change it out with a new one. If the weather is still cold when you clip your horse be sure to blanket him afterward.
a Halter
It's called a Bridle Path :)
There are many websites available from which one can find free clip art of horses. Horsecrazygirls and graphicsfactory are just two sites that offer many different horse clips.
Bridle Path
Bridlepath