weighting scales are used to measure the weight of an item. to use a scale, the item which needs to be weighed is put on one side of the scale. then, usually stones are put on the other side to compare the weight of the stone with the weight of the object you have chosen. if both cups are in the middle, it means that the weights of the objects are equal. if one cup is more up while the other one is down, it means that the one that is down is the heavier one. for example: if you place a small stone in one cup, and a watch in the other cup, and the cup with the watch goes down and the stone obviously goes up, it means that the watch has a greater weight than the stone.