A width Prominent on Thoroughbred type withers--well defined goes on narrow Arabs and Paso's, those with shoulders that blend into their sides.
B Width Horse has well defined withers, but is a dab thicker set, and shoulder may be more prominent. This works for many Arab's, Morgan's, Tennessee Walkers, Foxtrotter's, and some Quarter Horses.
C Width Accommodates a wider backed horse, but still of the breed type . . . Just a thicker set. Used more on Arabs, Morgan's, and Tennessee Walkers.
The above trees work best on horses whose backs slope away from the spine. The following are for flatter backed horses.
CC Width Like the C tree, but better for horses that are flatter over the back and loin. Also good if horse is slightly sway backed or bunchy shouldered, or whose croup is higher than withers.
D Width For the really thickset horse. Some of these individuals have good withers and top lines, some are very flat over the withers . . . All are broad over loin and back. It is the angle of the bars that makes this tree work. Ideal for Quarter Horses, and many of the new thicker Arabs, and quite a few of the BLM Wild Horses.
E Width For the horse that is very broad backed but requires flare.
F Width For the horse that is very straight backed but requires shoulder flare