- Locks at a certain angle and operates like a straight bar
- Locking mechanism takes effect when the horse gets strong or opposes the rider's hand
- Enables precise and effective rein aids due to acting on tongue, poll and lower jaw
- The leverage effect on the poll can be varied by different rein options
- Often used in combination with bit converters or with 2 reins (higher educated riders)
- Use of a curb chain guard is recommended to protect the sensitive lower jaw bone