Road Studs are a craftable item. Users in the Blacksmithing stream can craft it using iron and magnesium.
Course Article
Improving Traction for Dressage Horses
Dressage horses don't often leave their perfectly manicured sandboxes, but sometimes they might find themselves competing in slippery conditions. Most commonly, dressage horses may be competing on short grass with a hard underlying surface that can be slippery when turning or performing more advanced movements. Even the sand arenas, particularly after very hot days, can also become quite hard-packed, so caulks may help in those situations as well.
The main way to add traction to a horse's footing is by adding caulks (also known as corks or studs). Most caulks are screwed into the shoe, so they can be removed between competitions. This is particularly important because some caulks are very sharp, and can cause a lot of damage if the horse steps on itself!
One of the main types caulks used for dressage horses are road studs, which are a small square-shaped stud. This helps give traction on hard-packed ground.
In Oxer To Oxer, road studs can be applied to a horse's shoes to give them a one-time increase in a random dressage stat.