These are iron horse harness parts with U-shaped curves. The bottom portion connected to a large harness around the horse, while the relatively straight portion at the other end faced upwards. The upward-facing portion has a socket where a flagpole was inserted, so the horse could carry a flag behind a rider. This use of metal flag holders for horses is depicted in the wall paintings of the Complex of Goguryeo Tombs (located in present-day North Korea; built during the Three Kingdoms period of Korean history, approximately the 1st-7th centuries C.E.) and through haniwa excavated from the 14th Sakamaki Kofun in Gyoda City, Saitama Prefecture. In Japan, these metal flag holders are extremely rare artifacts.