Square nails are a type of fastener characterized by their square-shaped shaft and head. They were commonly used in construction and woodworking before the introduction of round nails. The design of square nails allows for a stronger grip in wood, making them ideal for heavy-duty applications. Historically, square nails were hand-forged, which made them a popular choice in the Colonial America era. Today, they are often used in restoration projects to maintain the authenticity of historic buildings and furniture. While less common in modern construction, square nails remain valued by craftsmen and woodworkers for specific applications.