Pencils are a writing utensil used for writing and drawing. Modern pencils usually consist of a graphite/clay core encased within a wooden cylinder. Modern pencils are constructed by finely grounding the graphite and clay into powder form then, adding water and firing them in a thermally insulated oven, or kiln. Once melted in the kiln the mixture is produced into long strings with are inserted into a pre-cut plank of wood with grooves cut out. Another plank of wood is glued on top of the other holding the graphite.
Pencils are commonly classified based on their "hardness'. "HB" is the hardness most commonly associated with what is called a No. 2 pencil in the U.S. The "H' standing for hard, and "B" for black. Pencils are available in wide variety of hardness. One should choose hardness carefully for each application as there are twenty different gradients to utilize from F to 9B.