Title: Demystifying the half halt
Subtitle: My horse snatches at the reins after a series of half halts.

Case: An amateur dressage rider preparing for a schooling show.

Question: The way my trainer has explained a half halt to me is a squeeze on the outside rein, followed by one on the inside if needed to check tempo and rebalance. My horse now snatches at the reins and objects. What is wrong?

To be totally honest, there is some confusion even in the higher level riders about what constitutes a half-halt. Unfortunately, in this country many riders/trainers do not differentiate between a half-halt and a half-halt on the rein. These are two distinctly different aids and are used for different things. Many times the upper level riders are so accomplished in the half-halt that they no longer realize the importance of learning the aid. It comes naturally to them.

Your level of training and heavy-hands indicate to me that you are trying to control the speed (cadence) of the gait, rather than rebalance your mare. This requires the half-halt from the seat which is, to use the European term, a more gross (bigger, larger, more aggressive) aid than a half-halt on the rein which is a subtle rebalancing aid. If you try to use the latter when you need the former, you can run into a problems such as snatching at the reins or head-tossing.

To understand a true half-halt it helps first to understand the halt. The full halt comes from the lower back. Stiffen the lower back and exhale to "sink" into the saddle and to stop your motion. Your leg is in "neutral" and is not asking for forward. The horse can't help but halt. Only if absolutely necessary (and it should hardly ever be necessary), add a slight squeeze of the ring fingers equally on both sides to augment the seat aids when the horse has HADD (Horsie Attention Deficit Disorder.)

The half-halt is sort of a baby halt. The easiest way to understand a half-halt is to school yourself into it in the following manner on a 20 meter circle:
Ride a nice working trot until the horse is very relaxed and working with a soft back.
Then begin halting once on the circle: a full halt from trot using the seat aids described above.
After a pause, ride on at the trot never allowing walk steps either into the halt or out of it.
School in both directions.
(You may need several days of this just to get you both comfortable with the halt from trot and trot on. Take your time. Use the schools to improve your halt aids and make yourself consistent. Try to use no rein aids in the halt. Refine your "trot" aids so that each time you ask for trot with your leg the horse knows precisely what you want. Work on your balance. Don't rush. Patience now will pay off later!)

Once you are halting and trotting on happily in both directions from different points on the circle so the horse doesn't anticipate always halting in the same place, the next steps toward half-halt are:
Ride the exercise as above but
Each time you halt, make the period of time you are actually halted smaller and smaller.
(Remember not to rush the halt aids and make sure you are being consistent. Work at this over a series of days so that there is no frustration and you have the time needed to get yourself consistent.)
Eventually, with patience and relaxation you'll ask for the halt but immediately ask for forward trot.
(The aids will be very nearly but not quite simultaneous.)
The horse will slow within the gait from your seat but she won't halt and the trot after the aids will be terrific.
THAT is a half-halt.

Remember that this is a very VERY difficult thing to accomplish but it is a basic tool that you must have to ride Training Level tests.

The half-halt on the rein comes later. The rebalancing with a SLIGHT squeeze of the ring finger on the outside rein and/or the inside rein is an effective aid for rebalancing and collecting once you have true seat. When your seat is one with the mare all the time and you can feel which foot is on the ground and which foot is off the ground, when you can use subtle and consistent leg aids and your balance is excellent (including good balance during a correct half-halt) then you can add the half-halt on the rein to rebalance.

Please always remember and never forget (!) that rein aids come from the ring fingers and no other part of the hand. The rest of the hand remains soft as if you are cradling two baby birds.