In violin and bow building, the frog refers to the movable lower part into which the hair is inserted. Originally, the frog was made of wood, ivory, bone, tortoiseshell or horn. Woods that can be used include ebony, snake wood and palisander, though ebony is used most often. The metal pieces of the frog such as the ring, track and knuckle were developed over the course of time and added to increase the life span of the frog. Here on our page you can find a cross-section of a modern frog and its mechanics.