The intricately carved seals of the Indus Civilization were probably used in trade. Typically square with each side measuring from two to five centimeters, the obverse of most seals was engraved with mythical scenes or animals and an average of five Indus script signs. The square seals also had a small boss on the back through which a string or a cord had been passed, allowing them to be worn or otherwise secured. While the Indus script remains undeciphered, approximately 400 signs have been identified thus far in what was probably a logo-syllabic writing system in which the signs were read from right to left.