Wet your horse’s back and saddle area with water before riding. Saddle your horse without using any pads. Ride through your normal paces (e.g., walk, trot, canter) for about 10 minutes. Dismount, untack, and make note of what areas on your horse’s back are dry or dry first. These are receiving the most pressure from the saddle.
The theory is that the saddle leather absorbs the water from the horse’s coat. The harder it presses against the horse’s back, the more water it’s likely to absorb.
Take note of your horses back each time you remove your saddle after a ride.