'COSS' is the a tool which is consist of four stationary supplies, a pen, a sharp pencil, a knife, and a ruler without a case. Each part not only can be easily separated, but also can be the one tool using magnet which is embedded in each supplies. Also, each tool is square shaped so that can be gripped easily. Especially, square shaped knife is easier and more safe to use than rounded one, because rounded shaped knife can be slippery so that can be dangerous for user.