Why would someone use a curb strap on a snaffle bit when a snaffle bit does not work off of leverage? For safety of course! The strap keeps the bit centered in the horses mouth, and prevents the bit from sliding through the horses mouth when you pull on one side. A curb strap when used with a snaffle should never be made of chain, it moves too much, and can bang on your horse’s chin and drive him crazy. Also, if the bit does get rotated in the mouth the chain could injure your horse’s lips or bars of his mouth. So, stick to leather, nylon, string, or even baling twine ( not wire) for your curb straps. Your strap should be adjusted so it can not flop over his chin, but not so tight that is makes contact with the curb area of your horse’s jaw, and put unnecessary pressure on the bit. Your reins should attach behind the curb strap, just like the drawing shows.