The wheels

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Across
  1. 4. wheel fixed to a wagon to carry heavy loads
  2. 5. buying and selling activity
  3. 6. Earliest wheel type made of wood and used under heavy loads
  4. 8. Point about which a wheel turns
  5. 9. Thin rods that make a wheel lighter
Down
  1. 1. wheel that shapes clay
  2. 2. Round invention that changed history
  3. 3. Office furniture that still uses tiny roller wheels
  4. 4. Heavy‑load vehicle pulled by oxen
  5. 7. Cylindrical tree pieces that inspired the first wheels