Graphite pencils are writing instruments that use a core made of a mixture of graphite and clay. The graphite provides the dark mark on paper, while the clay helps to control the hardness of the pencil. Pencils are graded on a scale from hard to soft, with "H" indicating hard and "B" indicating black or soft. The most common pencil is the #2 pencil, which is often used in schools and standardized tests. The outer casing of a graphite pencil is typically made of wood, although some are made from recycled materials or plastic. Pencils can be sharpened to expose more of the graphite core, allowing for finer lines. They are a popular choice for drawing, writing, and sketching due to their ease of use and erasability with an eraser.