Aboriginal people did not usually build houses, except huts of grass, leaves and bark. They did not usually build walls or fences, and there were no horses, cows or sheep in Australia that needed to be kept in pens. The only Aboriginal buildings that are known are fish-traps made from stones piled up in the river, and the remains of a few stone huts in Victoria and Tasmania. The Aboriginal people did not use metal or make pottery or use bows and arrows or weave cloth. In some parts of Australia the people used sharp flaked-stone spearheads, but most Aboriginal spears were made of sharply pointed wood. Australia has a lot of trees that have very hard wood that was good for spear making. The boomerang was used in some areas for sport and for hunting.