business purposes. Mitome-in and lesser seals are usually stored in inexpensive plastic cases, sometimes with small supplies of red paste or a stamp pad included. Most Japanese also have a less formal seal used to sign personal letters or initial changes in documents; this is referred to by the broadly generic term hanko. They often display only a single hiragana, kanji ideograph, or katakana character carved in it. They are as often round or oval as they are square. They vary in size from ; women's tend to be small. Gagō-in are used by graphic artists to both decorate and sign their work. The practice goes back several hundred years. The signatures are frequently pen names or nicknames; the decorations are usually favorite slogans or other extremely short phrases. A gago in can be any size, design, or shape. Irregular naturally occurring outlines and handles, as though a river stone were cut in two, are commonplace. The material may be anything, though in modern times soft stone is the most common and metal is rare. Traditionally, inkan and hanko are engraved on the end of a finger-length stick of stone, wood, bone, or ivory, with a diameter between . Their carving is a form of calligraphic art. Foreign names may be carved in rōmaji, katakana, hiragana, or kanji. Inkan for standard Japanese names may be purchased prefabricated. Almost every stationery store, discount store, large book store, and department store carries small do-it-yourself kits for making hanko. These include instructions, hiragana fonts written forward and in mirror-writing (as required on the working surface of a seal), a slim in tou chisel, two or three grades of sandpaper, slim marker pen (to draw the design on the stone), and one to three mottled, inexpensive, soft square green finger-size stones. In modern Japan, most people have several inkan. A certificate of authenticity is required for any hanko used in a significant business transaction. Registration and certification of an inkan may be obtained in a local municipal office (e.g., city hall). There, a person receives a "certificate of seal impression" known as . The increasing ease with which modern technology allows hanko fraud is beginning to cause some concern that the present system will not be able to survive. Signatures are not used for most transactions, but in some cases, such as signing a cell phone contract, they may be used, sometimes in addition