It is a graphical identity obtained by a person through symbols or letters that may or may not correspond to his name which gives authenticity to document. The signature is generally a person's most common writing act. And it is largely habitual. As there are no rules for devising and producing signatures, they are highly individualized according to each person's mental design. Often deliberately formulated, the person's signature serves as a "TRADE MARK". Signature can be written as illegible shapes or series of clearly decipherable letters that distinctly spells out the person's name. in many cases they have no resemblance to the writer's name at all, but they are merely identifying marks. In any case their construction and execution are relatively stable and their features more or less subconsciously produced. Due to their repetition writing strokes and formation that comprise person's signature are generally consistent, even over long time spans.