This is how you do it:

"Start by building a course according to the sketch below. 

Take your time and ride the course at a slow pace to get a feel for the canter and the distances. If something doesn't feel quite right, redo it until you get it 100% right. 

While the distances can be varied, I recommend practicing the stride length that will be required in competition (provided you compete, of course.) 

This exercise helps you find a good rhythm and the correct stride length in a jumping course."