What is a 'penny' rating used to measure?

NAIL SIZES are designated by 'd' (penny). The 'd' abbreviation comes from the Latin DENARIUS (a Roman coin) because early nails were sold by their cost in pennies per hundred. Common nail sizes (length in inches): 2d equals 1 inch; 3d equals 1.25 inch; 4d equals 1.5 inch; 6d equals 2 inches; 8d equals 2.5 inches; 10d equals 3 inches; 12d equals 3.25 inches; 16d equals 3.5 inches; 20d equals 4 inches; 30d equals 4.5 inches; 40d equals 5 inches; 50d equals 5.5 inches; 60d equals 6 inches. Most commonly used in framing: 8d for sheathing, 16d for framing studs to plates. The penny designation is for length only. NAIL TYPES AND APPLICATIONS: COMMON NAILS have full-diameter shaft and flat head; for framing and general construction; sturdy, hold well. BOX NAILS are thinner than common nails of same length; less likely to split wood; for siding, fencing, sheathing. FINISH NAILS have small unobtrusive head (cup-shaped); for trim, cabinets where you don't want the head to show; head countersunk slightly below surface, filled with putty. CASING NAILS are larger than finish nails with slightly larger head; for window/door casing. BRADS are very small finish nails (18 or 23 gauge); for small trim, picture frames; usually shot from brad nailer (pneumatic). ROOFING NAILS have wide flat head; galvanized for rust resistance; for shingles, felt paper; sized 7/8, 1, 1-1/4 inch; head pulls into shingle to hold. DRYWALL NAILS have bugle head, ringed shank for grip in framing through drywall; alternative to drywall screws. MASONRY NAILS are hardened steel for nailing into concrete/brick. DECK NAILS are galvanized or stainless for outdoor use; corrosion-resistant; ringed or spiral shanks for better grip. SPIRAL/RINGED SHANK NAILS are twisted or with rings; better holding power; especially for siding, decking, framing in seismic/wind zones (resist withdrawal). MATERIALS: STEEL is bright (uncoated, indoor only — rust), galvanized (zinc-coated, outdoor/treated wood), stainless steel (premium outdoor); ALUMINUM is for aluminum siding (no galvanic corrosion); COPPER for copper roofing; BRASS decorative. NAIL HEADS: full-size flat heads hold larger area (for plywood, sheathing); checked heads (cross-hatching) for grip; bugle head for drywall; convex/cup heads for finish nails; no head for double-headed nails (for temporary construction; pull out easily). NAIL GUNS (PNEUMATIC NAILERS): use compressed air to drive nails; types: FRAMING NAILER (driving 16d framing nails), FINISH NAILER (15 or 16 gauge for trim), BRAD NAILER (18 or 23 gauge for small trim), ROOFING NAILER (coil-fed for roofing nails), SIDING NAILER (galvanized box nails for siding). Battery-powered cordless options also available. SAFETY: never point at people; never carry with finger on trigger; wear safety glasses (ricochet hazard); use SEQUENTIAL TRIP (not bump-fire) for accuracy; bump-fire can cause double-fires when accidentally striking. NAIL vs SCREW: nails install faster (especially with nail gun); better in shear (sideways forces) which makes them good for framing; cheaper; screws have superior pull-out resistance, slower installation, more secure for things expected to be disassembled.