Precision Proportional Dividers are constructed from Duralium, a lightweight alloy that allows accurate engraving of increments. These dividers are designed to assist the user to divide lineal measurements in to equal increments at predetermined ratios. By choosing the ratio engraved on the instrument the distance between the points at one end will differ by that ratio at the other. For example if a ratio of 3 to 1 is chosen and the points at the longer end are opened to 150mm then the distance between the points at the shorter end will be 50mm. A reduction or enlargement of a dimension can therefore be transposed.