Which bit type is commonly designed with slots for rein attachment to enhance leverage?

The Pelham bit is specifically designed with slots for rein attachment, which is a crucial feature that enhances leverage during riding. This design allows the rider to attach the reins in different positions depending on the level of control and communication they desire with the horse. When the reins are attached in the lower slot, it provides a more severe leverage and can increase the bit's effectiveness for certain training or performance situations. Conversely, attaching the reins to the upper slot can offer a gentler feel.

This versatility in rein attachment makes the Pelham bit particularly valuable for riders who want to adjust the pressure and leverage applied to the horse's mouth, depending on their needs and the horse's responsiveness.