Scribers are hand tools used in the metal trades to mark lines on workpieces, prior to machining. This is used instead of pencils as the marks from pencils cannot be seen as clearly as Scriber marks. They consist simply of a rod of high-carbon steel, in its hardened state, that has been sharpened to a point at one or both ends. They are used by drawing the point over the surface of the workpiece to leave a shallow scratch on its surface.
Due to the nature of metal, and the accuracy generally sought after when machining it, a thick pencil or ink line would either be impossible to lay down accurately or prone to erasure during the machining operation. The crisp, bright mark exposed by the scratch of a scriber is semi-permanent and thin.