Using grids of trotting poles has advantages for all horses, whatever discipline they compete in, as they help develop greater engagement, strength, balance and regularity of stride.

For this exercise start with three trotting poles and then build up to six to eight poles. Remember that working through trotting poles is hard work, especially when the grid is longer and the poles are raised. Start over the three poles and then build up as your horse becomes proficient and is able to maintain the same regular rhythm in his trot.

HA2362Bob Atkins
Right: You can see this horse is quite active over ordinary trotting poles.

Once he can do this, raise one end of alternate poles and work through the grid. Remember to approach off both reins - the objective is to keep the same active pace over all of the poles. Your aim is to have all the poles raised - just a couple of inches off the ground initially - and to keep the same regular activity throughout the exercise.  
You can have the poles four or five inches off the ground which requires considerable concentration from horse and rider and requires your horse to use more energy. Do not attempt this until your horse is very proficient at trotting over slightly raised poles.