trotter
A horse that moves at a trot, that is, alternately lifting diagonal pairs of feet off the ground; the trot is slower than the pace.
breast collar 
Part of the harness that goes around the horse’s neck; it transmits the horse’s movement to the shaft.
knee boot 
Rigid equipment that protects the horse’s knee.
shin boot 
Equipment placed around the cannon of the horse’s leg to protect it from injury.
sulky 
Two-wheeled one-passenger vehicle that is pulled by a horse; it is light (around 35 lb), aerodynamic and has no body.
driver 
Person who steers the horse; the driver’s main task is to restrain the horse to conserve its energy for the right moment.
handhold 
Rein that is held by the driver to control the movement of the bit and thus steer the horse.
shaft 
Wooden or metal arm that extends the sulky; the horse is harnessed between the two of them.