Fitting your harness to your horse might seem to be a simple thing to do. But in reality, it is an ever evolving process.
The first time you will fit your harness to your horse is when you are training him to drive. Most new horses to driving have never had a harness on them, so the process of dressing the horse must be slow and methodical.
The first part of the harness to be put on your horse is the saddle, with the girth, back strap, crupper and breeching attached. As when you saddle a riding horse, the first thing to do is place the saddle on the horse. The saddle should set about two to three inch behind the withers. As you place the saddle, let the back strap and breeching drop down over the horses butt. Now, cinch the saddle in place so that it will not fall off. This does not need to be gut wrenching at this time. Be sure that the back strap is flat and down the center of your horses back, and the breeching is even on both sides of the horse. Now carefully lift the horses tail so that the breeching is under the tail and touching his butt. If your horse has never had a crupper strap on, than now is the time to be careful and proceed with gentleness. Gently hold the dock of his tail up just a couple of inches and slip the crupper strap under and around the tail, then gently put his tail back down. If he is okay with this, then buckle the crupper loosely, at this point you don’t want to give him a wedgie.
The other part of the harness that you need to put on your horse, when you are training him is the bridle. First thing to do is put on a bit that your horse is used to. Most driving horses are started in a drop cheek snaffle. If you ride your horse, then match the driving bridle to his riding bridle to get the bit at about the right length. Undo the nose band and put the bridle on just as if it were your riding bridle. Take it slow as the blinders will be a new item for the horse. If your horse is okay with his driving bridle, then adjust the blinders so that his eye is at the center of the blind. You can adjust the side straps, as well as the crown buckle, to do this. Now adjust the bit so it sits properly in his mouth. Then buckle the nose band leaving enough space for two fingers between his skin and the band.
You are now ready to start your horses ground driving in preparation of him eventually pulling a carriage. As the days go by and your horse gets comfortable with his new tack, you will be able to buckle the crupper tighter along with the girth.
For the horse that is an accomplished driver, the process of dressing him when you as the new owner go to hitch up the first time is easier. If your harness is new, be sure it is totally put together ahead of time.
Again you start your process with placing the saddle with the back strap and breeching attached over the back of the horse with the saddle two to three inches behind the withers. With the trained driving horse, you will start by placing the crupper under the horses tail and buckling it. Then you will adjust the saddle to the appropriate place and adjust the back strap so that it is straight and not floppy. Adjust the breeching so that it sits at the level of your horses stifle.
Next comes the breast collar with the false martingale and neck straps attached. Holding the breast collar on one side of the horse, toss the neck strap over the wither and attach it to the breast collar. The breast collar should sit about two inches below where the horses neck connects to his body. If to high it will interfere with the horses breathing. Toss the traces over the back of the horse so he will not step on them. Bring the false martingale between the legs and run the girth through the loop on the end, then buckle the girth.
Now, put the bridle on the horse and buckle the nose band and the throat latch. The throat latch needs to be tight enough that the horse will not be able to catch it on anything and remove his bridle, but not so tight that he can’t move his head properly. Lastly, run the reins back through the terrets on both the shoulder straps and the saddle, then buckle the reins together.
You are now ready to hitch your horse to your carriage. Have a helper head your horse and you bring the carriage up to the horse. Remember to talk to your horse while doing this, as he can not see you when you are to the side or behind him. Place the shafts in the tugs. The shafts should not extend past the horses shoulder. Bring the traces back and connect to the singletree. The traces should be taunt and not droop when the horse is pulling. If they are to long then adjust to fit properly. Buckle in traces make it easier to fit the horse.
Run the breeching wrap straps through the D-ring on the shaft, wrap around the shaft one to three times and then buckle. After you do this on each side the same, there should be enough room for your fist to fit between the breeching and the butt of the horse. Too tight and it would be like you riding the brake and too loose would be like having no brakes.
Buckle the tug down with the strap if you have French tugs, or wrap the wrap straps if you have traditional tugs. On a four wheeled carriage, they need to be just tight enough to keep the shafts in place at the sides of the horse. On a two wheeled cart they will need to be tighter as to hold the entire cart down. If too loose when you enter the cart and sit down the shafts will rise up and the cart could tip “they must be snug”. You are now ready to get in and drive your horse.
I have always had a harness for each of my horses. The reason for this is that it is much easier than trying to readjust the harness every time it is put on a different horse. Even with each horse having his own harness, it does not mean that it will always fit the same. Over time your horses shape will change as he grows, and his conditioning will change how his body looks. Because of this, you will always need to adjust as the time goes by. One example is with synthetic harness, it will stretch over time and you will need to adjust for that stretch. This happened with my Friesians bridle to the tune of one inch longer on the bit straps.
I have always told my students that when they are at a show to never change their harness even if the judge, TD, or other competitor or trainer says it should be a different way. Always show just as you practiced at home because that is what the horse is used to. If you want to experiment with adjustments the place to do that is at home not a competition. So just tell the helpful people that you will take it under consideration.
The other thing you will see is that many drivers harness in many different ways. For example, some will wrap the too long traces around the shafts and others you will see them bring the back breeching straps and put them through the loop at the end of marathon shafts. These are the worst things one could do. The wrapped traces take the play out of them, making pulling the carriage harder for the horse because they are not pulling off of the singletree that does move. When you run the breeching straps through the loops on the end of the shafts, you are basically making an enclosed box that the horse now is confined in. The distance from the front of the shaft to the butt of the horse is all the horse has to work with. So his body and legs are confined to that space. This is not a good scenario for doing Dressage. Every time you ask the horse to go forward, the breeching hits against the horses butt and brakes the carriage, so you are telling the horse to go and stop at the same time.
Harnessing is the major component for connecting your horse to your carriage or cart so it needs to be correct and safe for both the horse and you.