The TSD-3 is a modification of the Cornell™ Collar designed for harness race horses (trotters or pacers). 

The TSD-3 should be used only after your veterinarian has diagnosed an upper airway problem such as dorsal displacement of the soft palate that is likely to be improved by positioning the larynx (voicebox) in a more forward and upward position that has been shown to be beneficial in stabilizing the upper airway during strenuous competition.

It is comprised of a head strap with lifting mechanism and a race caveson. The lifting mechanism, must be placed just behind the depression formed by the basihyoid bone (consult your veterinarian). The lifting mechanism is then secured forward to the caveson. 

A tongue-tie may be applied as well but is not usually needed.

Step 1. The caveson is placed and adjusted so that the noseband is approximately halfway between the facial crest and the corner of the mouth. Do not tighten the caveson at this time. (Figure 1).

Step 2. Put the crown piece of the head strap over the poll and place the head strap so that it rests immediately in front of the ears across the brow. Then place the tip of the lifting mechanism in the depression just behind the hyoid bone on the midline between the jaws (Figure 2). You can identify this depression by placing a fingertip at the “*” and moving it backwards along the bottom midline. Place the tip of the lifting mechanism immediately behind the first bone felt. Tighten the head strap buckle so that the tip of the lifting mechanism fits comfortably in this depression. Do not over tighten.

Step 3. Place the bridle on the horse and securely tighten the caveson. Pass the connecting straps under the crown straps of the caveson and buckle them to the straps from the lifting mechanism. Securely tighten the connecting straps ensuring that the tip of the lifting mechanism remains in position behind the hyoid bone. This is the action that exerts the desired effect on the larynx.

Step 4. Check that the tip of the lifting mechanism will remain in the correct position when the head is extended by lifting the nose. If necessary, adjust the tightness of the head strap.

Step 5. Secure all straps into their keepers. A final check should ensure that the tip of the lifting mechanism is still in the right location and that the head strap itself is quite loose and poses no risk of a choking hazard.

Precautionary statement: As for any device (bridle, halter, cribbing strap) with straps crossing over the throat area one must exercise care to not excessively tighten straps such that there is compression of the trachea (windpipe) or nasopharynx. Customary precautions for placement of equipment must be used---do not place this device over the nostrils so that there is obstruction of nasal airflow.