A means of crimping a brass shot shell case closed is necessary when reloading them. A tool commonly encountered is Kynoch’s design, patent G 609. These were copied by other companies, such as Lightwoods. In use, the double knurled end is screwed off (it doubles as a decapping base), and the tool is pushed over the mouth of the case. The ridges on the internal crimp start a star crimp, then the tool is inverted to close the case as the user wishes. The case is not fully closed, as an overshot card wad is used to contain the load.
These tools are also encountered in bore rifle and ball & shot gun sets, to secure a ball or bullet.