The smile line is the lengthwise point on a nail where the nail bed ends and the free edge starts, it is a half-circle that somewhat resembles a smile; also used to describe the artificial creation of the same line with acrylics, gels, or other enhancements. For many nail technicians, achieving the perfect smile line can be tricky. Generally, a smile line should mirror the shape of the cuticle, so if you were to bend the nails in half they should match. The sides should be just as high on each side, and the center of the smile line should be at its lowest point in the center of the nail. The shape should be centered, like the tip of a round nail should be.