Actvity Summary: This activity was created as a result of the blog about measuring being an underrated skill in science (released in EXP 393). In hard rock cores (samples from the ocean floor in the shape of a tube) sometimes have fractures that fill up with minerals. These fractures are called veins because they are filled and no longer an empty space. Scientists will measure these veins to know where they show up on the core, how long they are, and later find out what they are filled with. The direction of the veins can also help scientists estimate the direction of stress that caused the initial fractures to form. This is a quick introduction to using a ruler, understanding how to read a ruler, and how we can use a ruler to measure lengths of veins in basalt cores.