Rule/One is a pen and a ruler in one. The unit consists of five aluminium components and is lightweight yet still robust. At a length of 13 cm, it is easy to carry. The cap at the top end of the pen can be replaced with a removable lanyard. There is also a special tip for touchscreen devices – another practical feature of the tool. Neodymium magnets inside the ruler ensure that the pen stays securely in place.