Nails

Nails may refer to two distinct subjects: the keratinous coverings on the fingers and toes of vertebrates, and metal fasteners used in construction and carpentry.

Biological nails consist of the nail plate, nail bed, and nail matrix, with supporting structures such as the cuticle (eponychium) and the hyponychium. The nail plate sits on the nail bed and is produced by the matrix, a tissue under the proximal nail fold. The visible pale area near the base, the lunula, marks active growth. Nails are composed mainly of keratin and grow continually from the matrix.

Growth rates vary; fingernails typically grow about 2-3 millimeters per month, while toenails grow about 1 millimeter per month. Nails protect the fingertip pads and assist with fine motor tasks. Health indicators include color, thickness, and shape; changes can reflect infections, anemia, thyroid disease, or nutritional deficiencies. Proper nail care includes regular trimming, gentle filing, avoiding trauma, and keeping the area clean and moisturized.

Hardware nails are slender metal fasteners with a sharp point and a head, used to join materials such as wood or drywall. They come in various materials—including steel, stainless steel, copper, and aluminum—and finishes, such as galvanized or coated. Common types include common nails, finishing nails, box nails, brad nails, roofing nails, and masonry nails. Selection depends on substrate, load, and desired finish. Installation typically requires a hammer or nail gun, with care to avoid splitting wood and to drive the nail straight.

Nails have been used since ancient times; modern machine-made nails emerged in the 18th century, with galvanization increasing corrosion resistance.