Moai sculptures were erected to commemorate the deaths of chieftains and other notable persons. They were put on rectangular stone slabs known as Ahu, which are graves for the persons depicted by the sculptures. The Moai sculptures were intentionally made with a variety of characteristics in order to preserve the appearance of the person they represented. The Moai statues were purchased from a single group of carvers. The purchasing tribe would compensate with whatever they had in plenty. Sweet potatoes, poultry, bananas, carpets, and obsidian implements are instances of trade products. Because a larger monument would be more expensive, bigger sculptures would also imply greater grandeur for the tribe, as it would demonstrate that the people are intelligent and hardworking enough to pay.