I'm not savvy on tack but I'll try and explain it correctly. I have an 8 yr old mare I trail ride. I use a snaffle bit. My farrier said to get a D ring snaffle. I've always used the snaffle with the shanks on the outside of the mouth of which he said was too severe for an experienced horse. What's the difference and why is one used over another? Also, do I use a chin strap with the D ring? The farrier said I didn't need to. Any advice would be appreciated.