A taping knife is a flat, wide tool used in drywall finishing. It helps apply and smooth joint compound, also known as mud, over seams and imperfections in drywall. The blade is typically made of stainless steel or plastic, and it comes in various sizes, usually ranging from 6 to 14 inches. Using a taping knife is essential for achieving a smooth surface before painting or applying wallpaper. It allows for even distribution of the compound, making it easier to blend seams and create a polished finish. Proper technique with a taping knife can significantly enhance the quality of drywall work, ensuring a professional appearance.