There has been some confusion regarding the pinning area and defensive pins in a couple of the threads in this forum. I have created a representation of the diagram found in the NFHS rule book concerning the pinning area. I cannot post the one from the rulebook because of copyright restrictions. This is good representation of the area covered by the rule book. As you can see the area extends down to near the bottom of the shoulder blades which can be pretty far down for some wrestlers.

I did not post this thread in the Ask The Ref forum because of the rules there. As you can imagine what one ref sees as the bottom of the pinning area can differ from another, and each wrestlers pinning area can be larger or smaller depending on their size. Hope this helps