Originally Posted by Bluemoonlvr
Could someone help explain how to do this correctly and what aids need to be done.
The shoulder in
First it is a movement where the shoulders are moved onto the inner tract facing the inside of the arena ( if you have one). The horse bending to the inside ( but minimally) away from the direction of travel and the inside legs cross in front of the outside legs.
This is most easily achieved from the corner of the short side to along the length of the long side of the arena. The rider will have the outside leg slightly back to prevent the haunches from coming off the tract and the inside leg will be at the girth. If the rider waits for the horse to pass the corner a step or two and holding the natural bend that the corner would supply then they need to do little with the reins and should be able to hold the horse in place with their legs alone.
A half halt to ensure the horse maintains a lateral direction ( converts forward movement into a lateral one) and directs the horse to move laterally by their inside leg in unison with the horse crossing over.
Never should the horse be pulled into position by an overactive inside rein. The outside rein held quietly will prevent too much head/neck bend and be the supporting rein for the inside leg action.