Note: Our level rating system is different than Hanayama's. Hanayama's level 1 is equivalent to our level 5.... level 6 is equivalent to our level 10.
Back in America's Wild West days, cowboys used any means available to prevent their horses from being stolen. According to legend, one resourceful cowboy had the idea of rigging horseshoes to work as a lock, which served as the origin of this puzzle.
Hint: "Horses"