The breastplace prevents saddle from slipping back on horse. But be sure it fits: snug enough not to catch a hoof when jumping and not too tight to cut into the horse's muscles. Once on, you ought to be able to pull up the breastplate three inches above the neck OR fit your fist between the chest and the center ring of the yoke. The strap back to the girth must be slightly slack.
This is me at a horse trials. This breastplate allows his big shoulder to move, secures the saddle, and gives me something to hold onto!!
Hunting: (in photo, right) Yoke around neck and attached to D rings (remember to use Dee savers on your stirrup bars for the attachment) and to the girth. We apply snaps to the attachments for ease it putting on the breastplate. The traditional hunting breastplate is all leather. They can also have elastic on the yoke to allow for more shoulder movement to better rotate while jumping. A too tight breastplate not only inhibits movement but can pull the front of the saddle down, digging the tree points into the shoulder.
"A traditional hunting breastplate fits a wide range of horses and allows for shoulder movement." -Eventer Ashley MacVaugh (www.ashleymacvaugh.com)
Breast Collar: (photo, left) has a chest strap to prevent the saddle from slipping back and a strap over the wither to secure the collar in place. It attaches to the girth at the first billet and use a split-end girth to keep the straps from slipping low on the girth. The breast collar is more secure to hold the saddle than the traditional hunting breastplate. It is horizontal across the chest and not angled. When fitting, be sure it does not interfere with points of shoulders nor press on the windpipe. For correct fit, you must be able to slip a fist between the chest and the strap and fit a fist between the wither strap and withers.
Elastic Breast Girth: Attaches to dee rings (dee savers) on the saddle. Heavy elastic and has no wither strap. Least restriction to shoulders. It can be more snug than the breast collar. Placed at the base of the neck, be sure it does not press on the windpipe. Can be "Y" shaped and have an attachment from center of chest to the girth below the belly in addition to the billet attachments.
Elastic Y Fit Breastplate: Avoids pressure on windpipe due to the "y" shape which is similar to the traditional breastplate. The strap sits above shoulder and the elastic allows for a full shoulder rotation. It secures to the saddle at the D-rings, again it is advisable to use D-savers to prevent damage to your saddle, and snaps on the breastplate for ease of tacking up. The front strap goes between the front legs and attaches to the girth. For correct fit, you should be able to slip your fist under the ring at the center of the chest. Too tight and the breastplate not only inhibits range but also puts pressure on the tree points of the saddle.
"My choice for cross-country because it allows for complete freedom of the shoulder." -Robert Costello (www.tanglewoodfarmeventing.com)
Five-pointed Breastplate: Takes into account windpipes and shoulder movement. More moving parts for more movement. This breastplate attaches to Dee rings(Savers) and the first billet strap and from the center of the chest through to the girth. Lots of elastic for flexibility and sheepskin on the pressure points.
Martingales: Attachments to any of the breastplates or use the traditional running martingales.
Running Martingale: When you run the rein through the loop and hold it in your hand, the rein needs to be a straight line from bit ring to your hand. The martingale should not pull down on the rein or if it does, the length is too short. Remember rein stops so that the martingale rings do not run up to the bit rings.
Standing Martingale: attaches to back of noseband. You ought to be able to press the strap into the inside contour of the neck from it's attachment at the chest.