Also kakihan 書判, lit. written seal mark, or han 判. Specifically designed character representing or accompanying the signature and affixed at the end of letters and documents *okugaki 奥書. Originally, the kaō was used in place of a full signature, then came to accompany the signature and was written underneath it. The complicated pattern of brushstrokes (based on an abbreviation of Chinese characters or kanji 漢字) was meant to protect against forgery. One person may have used several kaō often changing the style with advancing age. In the mid-Heian period, kaō developed as a type of monogram, written in an abbreviated calligraphy *sōmyō 草名 which evolved from the custom of writing signatures in the formal style kaisho 楷書 (in the 7th century) and in the cursive script sōsho 草書 (in the 8th century). This style was mainly used by the imperial family. In the Kamakura period, the practice of combining elements of two characters in a name into a single written seal mark nigattai 二合体 developed, and was adopted by courtier and warrior classes. In the Muromachi period, kaō was often created from a single character related to one's name ichijitai 一字体. Around the 15th century kaō were created as original patterns unrelated to any character of one's name betsuyōtai 別用体. In the Edo period, the style of kaō was influenced by the 14th-17th century calligraphic fashion of Ming China, called minchōtai 明朝体. This was characterized by two horizontal lines (representing heaven and earth) drawn above and below the central abbreviated character.