Having clips on the bit end of your driving lines is risky business. Not only can it be a safety issue, but it can be very annoying to your horse, metal on metal is very irritating for some horses.
Why are they a safety issue? I have witnessed a draft horse that turned his head to bite at a fly and got the driving line clipped to his harness. It was not a pretty outcome once he realized he was stuck.
So, if your driving lines have a clip from the line to the bit, please just remove it and attach your lines directly to the bit.