Slobber straps are bits of leather that are used as an extra connection between the bit and the rein. They are used only in the western style of riding. (Rein chains, which I already talked about, are a similar idea).
Slobber straps are used for three reasons:
1. They reduce the wear and tear on the reins, especially on the trail - for example, when the horse drinks, the straps go into the water, not the more expensive reins.
2. They increase the weight of the reins, which when using the rein very lightly in the western style can add to the subtlety of cues.
3. Some reins don't attach to a bit easily.