I've been thinking a bit more about the C in the last post and how to go from a C (where the top of the C represents the left shoulder bowing out and destroying your "straightness") to a capital I (where the horse is straight and stepping underneath himself). When I first started to ride if the left shoulder was sticking out I'd want to pull on the right rein to try to correct. With hours of my instructor correcting me I have finally understood that its the exact opposite.
To help myself understand the why part I got out a chain today and layed it on the table in the shape of C. Grab the top of the chain and pull to the right to simulate pulling on the right rein. The chain follows the movement of your hand and the top becomes straight but horizontally straight, not verticial. The bottom of the C remains in the C shape.
The horse will do the same. Pull the right rein and the head will follow, causing the left shoulder to stick out even more. If you want the left shoulder to come back in and resume the straight track you need to provide pressure to that side - the same as if you "pushed" on the chain on your table.
So left shoulder sticking out requires a direct rein pressure on the left side. Doing so will pull the horses head to the left and in effect pushes the shoulder in.
Wow... this is hard to explain!
Another way that might help is think about when you are on the trail.
If you are coming up on a tree on your right and your horse decides to get way too close, what do you do? If you pull on the left rein, your horse's head will move away from the tree but his body will swing closer to the tree banging your knee straight into the tree. What you really want is to provide rein pressure on the right side (the tree side) and leg pressure on the same side. Your horse will bend around the right leg and your knee will be saved. Of course the left shoulder is bowing out then so after you pass the tree you will have to provide left pressure (leg and rein) to push the horse back to straight.
Any of that make sense? Hopefully not all topics will be this difficult to write about! I think I will tackle something easier next time!