Karuka, sakujo, komeya were the Japanese names for the ramrod used for loading muzzle loading guns.
The Chinese characters used for the word are seen very rarely in Japanese historical documents, and the word is most often written in katakana characters, then hiragana characters, then Chinese characters. Even when the word is written with Chinese characters, they are accompanied by furigana (Japanese characters showing how to read the Chinese characters), and after the Meiji period, the scholarly reading of the word tends to be sakujo following the Chinese reading style.
It was used not only for loading but also for cleaning the bore (Those that were strictly for cleaning were called washing arrows).
They were sticks made of wood or metal. When Japanese guns were using the matchlock system, bullets were loaded from the muzzle (muzzle loading method). The tool used to load ammunition was sakujo or alternatively called karuka. Until the mid 19th century, loading a gun was done mostly by this method. Even after guns developed to adopt breech loading, a ramrod was kept with certain guns, such as those for military use, for maintenance purposes.
Japanese matchlock guns had a tunnel-like hole in the wooden floor part of the barrel in order to install the ramrod, but since it was not sturdy enough to use for loading, another larger, more resilient one was carried with the gun during training. The ramrod that was attached to the gun was strictly for use in emergencies. Some guns with larger caliber did not have the hole for the ramrod and they were kept with a big oak stick made for the purporse. Ramrods that accompanied Western flintlock and percussion guns were made of steel. Some of the Japanese flintlock guns, such as Yonezawa-zutsu or guns used by Kanryu School of Shooting had ramrods made of steel but most ramrods were made of wood. Some of the guns used by Kanryu School had expensive ramrods that had elaborate gold inlays.