A prong is a narrow tab of metal, notched to fit a stone to secure it in a setting. Prongs are the most commonly used diamond setting, often used to display solitaire engagement rings. To create a prong setting, a diamond is inserted into three or more metal prongs that form a basket-like base. Prongs must be clipped to correct length. They need to cover the girdle and come up the crown approximately 50 percent of the distance between the girdle and the table.