Figuring out where the shoulder blade of the horse is relative to the bar of a saddle is more difficult than seeing it on a bare horse, because you not only have to figure out the bone under the skin, but also the bar under the leather.
Key points to remember in seeing the shoulder blade – the spine of the scapula is pretty much always visible unless covered by blankets, etc. and it is parallel to the muscle… https://www.rodnikkel.com/content/saddle-tree-blog-from-shop-and-desk/position-seeing-shoulder-blade-under-saddle-part-one/
Pictures, drawings and discussion showing the four major types of riggings used in saddles today.
The four common types of riggings commonly used today are the D ring rigging, O ring rigging, plate rigging and in skirt rigging. How the rigging is designed plays… https://www.rodnikkel.com/content/saddle-tree-blog-from-shop-and-desk/different-rigging-types-a-quick-explanation/