Most scholars consider the writing system to be an independent invention because it has no obvious connections with other writing systems at the time, such as Elamite, Akkadian, Hurrian, and Hittite cuneiforms. While Old Persian's basic strokes are similar to those found in cuneiform scripts, Old Persian texts were engraved on hard materials, so the engravers had to make cuts that imitated the forms easily made on clay tablets. The signs are composed of horizontal, vertical, and angled wedges. There are four basic components and new signs are created by adding wedges to these basic components. These four basic components are two parallel wedges without angle, three parallel wedges without angle, one wedge without angle and an angled wedge, and two angled wedges. The script is written from left to right.