sentences:  Common shapes of heads used in stone setting include round, oval, emerald cut, princess cut, marquise cut, pear shaped and trillian cut.V-shaped prongs are recommended for a marquise-cut or pear-shaped stone, while flat prongs are recommended for a flat-cut emerald.A prong setting holds the gem securely while allowing the gem to be struck with more light and from more angles, increasing the brilliance of the gemstone.