A pencil is an instrument for writing or drawing, usually consisting of a wooden rod with a core of mixed powdered graphite and clay. The mixture is extruded as a soft paste and placed in the grooves of two half-pencils which are glued together and dried. The term "lead pencil" comes from an early mistaken view that graphite is a form of lead. Pencils vary in hardness, the hardest (10H) containing the most clay, the softest and blackest (8B), the least. HB and F are intermediate grades.