These blades are the small knives mounted in the Kozuka (small handle). They are located in the side pocket of many saya (scabbards). These blades are often called Kozuka blades. They are usually tempered and were once polished on one side and have a sharpened edge on the other. There are usually file marks on the un-polished (signature) side. This side is sloped and is the side that is ground for sharpening. These blades are usually signed on the side with file marks.