16d

an abbreviation for "sixteen-penny" that indicates a nail that is three and one-half (3.5) inches (8.9 centimeters) long. "Sixteen-penny" applies to common, box, casing, and finishing nails. The term originates from the price per hundred nails; 16 pennies for 100 three-and-one-half-inch nails.

Alternate spellings and misspellings: sixteen penny nail, 16d nail, 16-d nail, sixteen-penny-nail