Kimblewicks offer the combination action of a curb chain with a snaffle bit. They are more severe in their action than a snaffle, because they have a leverage effect on the jaw, as well as the bars of the mouth. It is recommended that these bits always be used with a curb chain, which can apply pressure to the chin groove.
For those riders who wish to have extra control, without using two reins, Kimblewicks are a convenient alternative.