What is the purpose of keys in a snaffle with keys?

The purpose of keys in a snaffle with keys is primarily to introduce young horses to the bit. The design of snaffles with keys allows for added stimulation in the horse's mouth, helping them become accustomed to the feel of the bit. This is particularly beneficial for young or inexperienced horses, as the keys can provide a more gradual and comfortable introduction to the concept of accepting the bit while encouraging them to respond positively to the contact.

The other options, while they may be tempting to consider, do not align with the basic function and purpose of keys in a snaffle. For example, the idea that they create a more severe biting action is misleading since the key's role is not to increase severity but rather to facilitate a positive relationship between the horse and the bit. Encouraging strong control over the horse or preventing the horse from biting the reins also misinterpret the primary intention of this design. The use of keys in snaffles focuses on helping young horses learn and adapt to having a bit in their mouths rather than enforcing control or increasing discomfort.