Under the Ch'in dynasty, when axle lengths and the writing system were standardized, seals were subject to specific regulations stipulating the use of fine small seal script calligraphy. In the Han period small seal script was written in fuller, more homely, tidier calligraphy, and with the wider use of paper in the T'ang dynasty, chops became more commonly used in the manner of a signature.
秦朝專制，倡車同軌、書同文，印章規格各有定制，文取小篆細字；漢則崇尚樸實敦厚，印文中小篆文字較為豐滿、樸拙、工整；唐則因紙張普遍運用，印章可作為落款簽署之用，形制明顯加大。