Sumerians used sharp
I
to make symbols on clay tablets. (reeds/knives)

Reed

Explanation: In the Ancient Near East, clay tablets (Akkadian ṭuppu(m) ) were used as a writing medium, especially for writing in cuneiform, throughout the Bronze Age and well into the Iron Age. Cuneiform characters were imprinted on a wet clay tablet with a stylus often made of reed (reed pen).

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