Your horse's comfort is crucial when you are about to put weight on their backs. Weight in the wrong spot can cause nerve damage and excess pain for the horse.
The spine is very important to protect when using any type of saddle. All saddles must clear the dorsal spinous process. This is the highest part of the spine running along the horse's back. On an over weight horse it may actually be indented going down the center line of the horse.
Next to the spinous process is the transverse process. All the nerves and tenderness of the horse's spine is in between these points. The saddle can not hit these areas.
It's easy to find on a very skinny horse, but you should never ride a horse that is that skinny. When feeling for it on a normal or fat horse you will feel the hard spine (center), then off to the side will be a soft indentation that is the Multifidus.
Mark that spot on both sides of the horse's spine. The space between that is the channel width that you need for your saddle.
When looking at the saddle you can see the channel from the back and when you flip over the saddle. When viewing from the front you will also see the gullet angle and extra padding along the scapula.
DP Saddles that have the ultra flex tree and adjustable gullets actually have an adjustable gullet width. As you use the 10mm Allen wrench to adjust the DP saddles the wider you go the wider the channel and the more narrow you go the narrower the channel. Notice the space around the three fingers in the two left photos. In this particular model, Majestro Dressage with 8cm gullet, the 3 fingers are slightly touching the narrow setting and on the wide setting there is room for 2 or more fingers in the channel at that same point. Each model has a different range of adjustment to the channel. Talk to our trained saddle fitters to make sure you are getting the correct saddle for your horse and you.