http://www.sustainabledressage.com/tack/gadgets.php
Please Note!
This chapter is about the inventions of riders and saddlers, the things that are created and used to get the head down. They all do the same thing - limit the height of the head of the horse, and leave him to figure out how to deal with the pressure that they create. Hopefully, the horse will discover that to lower the head will make it go away.
I want riders to know that there are other ways. I want riders to understand that it's not about mechanically getting the head down - it's about stretching the neck out to stretch the back and make the horse "decontracted". And there are other options to accomplish that.