Bits work on seven areas of communication
1 The corners of the lips
2 The bars of the mouth
3 The roof of the mouth
4 The tongue
5 The poll
6 The nose
7 The curb or chin groove
This has much more movement than a fixed cheek or eggbutt, and can discourage the horse from fixing and leaning and encourages mouthing
This keeps everything stiller in the mouth – it can encourage horses to stretch into the contact
When you take a contact, it causes poll pressure and reduces pressure in the mouth – particularly useful for sensitive mouths as well as having a head lowering action.
This reinforces the turning aids and stops the bit sliding over the tongue and bars of the mouth – if you use bit keepers to fix the upper cheek of the bit, this stabilises the bit and will cause some poll pressure.