<P> A wide range of steels are used in reproductions, ranging from carbon steels such as 1020, 1040, 1060, 1070, 1095, and 5160, stainless steels such as 400, 420, 440, to high - end specialty steels such as L6 and D2 . Most cheap reproductions are made from inexpensive stainless steels such as 440A (often just termed "440"). With a normal Rockwell hardness of 56 and up to 60, stainless steel is much harder than the back of a differentially hardened katana (HR50), and is therefore much more prone to breaking, especially when used to make long blades . Stainless steel is also much softer at the edge (a traditional katana is usually more than HR60 at the edge). Furthermore, cheap swords designed as wall - hanging or sword rack decorations often also have a "rat - tail" tang, which is a thin, usually threaded bolt of metal welded onto the blade at the hilt area . These are a major weak point and often break at the weld, resulting in an extremely dangerous and unreliable sword . </P> <P> Some modern swordsmiths have made high quality reproduction swords using the traditional method, including one Japanese swordsmith who began manufacturing swords in Thailand using traditional methods, and various American and Chinese manufacturers . These however will always be different from Japanese swords made in Japan, as it is illegal to export the tamahagane jewel steel as such without it having been made into value - added products first . Nevertheless, some manufacturers have made differentially tempered swords folded in the traditional method available for relatively little money (often one to three thousand dollars), and differentially tempered, non-folded steel swords for several hundred . Some practicing martial artists prefer modern swords, whether of this type or made in Japan by Japanese craftsmen, because many of them cater to martial arts demonstrations by designing "extra light" swords which can be maneuvered relatively faster for longer periods of time, or swords specifically designed to perform well at cutting practice targets, with thinner blades and either razor - like flat - ground edges or even a hollow ground edges . </P> <Ul> <Li> Amakuni legendary swordsmith who supposedly created the first single - edged longsword with curvature along the edge in the Yamato Province around 700 AD </Li> <Li> Akitsugu Amata (1927--2013) </Li> <Li> Hikoshiro Sadamune (1298--1349) </Li> <Li> Kanenobu (17th century) </Li> <Li> Kenzō Kotani (1909--2003) </Li> <Li> Masamune (c. 1264--1343) </Li> <Li> Muramasa (16th century) </Li> <Li> Nagasone Kotetsu (c. 1597--1678) </Li> <Li> Okubo Kazuhira (born 1943) </Li> <Li> Shintōgo Kunimitsu (13th century) </Li> <Li> Masamine Sumitani (1921--1998) </Li> </Ul> <Li> Amakuni legendary swordsmith who supposedly created the first single - edged longsword with curvature along the edge in the Yamato Province around 700 AD </Li>

What is the wavy line on a katana